If you're struggling to know your PCRs from your CDCs from your PPEs, you're not alone.

Luckily CNN Travel is here to help you unravel the rat's nest that is the constantly changing world of global travel restrictions.

Come to these round-ups each week to learn about the countries relaxing entry rules, the attractions reopening the doors and the places that have shuttered because of Covid-19 outbreaks.

Explainers explained

Our travel elves have been working around the clock to put together explainers on all the latest twists and turns in travel guidance.

In Europe or hoping to travel there? The EU Digital Covid Certificate -- known informally as a "Covid vaccine passport" -- will be issued by July 1. CNN Travel gives you the lowdown here on who's eligible, how to get one, and which countries have started using it.

In the United States? The US Centers for Disease Control and Prevention (CDC) has issued new travel advice for more than 120 countries. Thirty-three destinations -- including Iceland, Israel and Singapore -- have moved into the lowest risk category. Find out more here.

Cruise news

On board Celebrity Millennium, part of the Celebrity Cruises group.

Celebrity Millennium -- the first major cruise ship allowing American passengers since the pandemic began -- set off last weekend from Sint Maarten. Its first port of call was Barbados, which is now welcoming fully vaccinated travelers.

However, it wasn't all plain sailing. Two guests had to be put in isolation after testing positive for Covid-19 in required end-of-cruise testing. And in in the Mediterranean this week, two passengers also tested positive for Covid on the MSC Seaside cruise ship.

Royal Caribbean International has announced that six of its ships will sail from major US ports in Florida and Texas beginning in July and -- further ahead -- a cruise themed around '90s sitcom "Friends" will make its debut next year.

It'll depart from Florida in May 2022 with a select 500 guests on board a 2,800-passenger ship. However, the most on-brand sitcom-meets-cruise adventure is still "Golden Fan at Seas," a celebration of "The Golden Girls," which is also set to return next year.

Luxury barging specialist European Waterways plans to resume barge cruises this June. It serves nine countries, including France, Germany, Holland and Italy.

Meanwhile, Uniworld Boutique River Cruises will resume operations on June 20 with a range of itineraries in Italy, Portugal and France.

The latest from Europe

Tourists walk toward the Erechtheion on the Acropolis hill in Athens on June 4.

The EU has a white list of countries from which nonessential travel into the bloc is approved: Israel, New Zealand, Rwanda, Singapore, South Korea, Thailand, Japan and Australia.

While the European Union is trying to create more universal requirements for tourism, conditions of entry differ from country to country.

Spain opened to vaccinated travelers from outside the EU on June 7 while France opened in international travelers on June 9 (the same day as it resumed indoor dining and the national curfew moved to 11 p.m.)

Those on France's "green list" -- vaccinated travelers from the European Union, Australia, South Korea, Israel, Japan, Lebanon, New Zealand and Singapore -- can enter restriction-free. Nonvaccinated travelers will need to do a Covid test.

Vaccinated travelers from the "orange list" -- which includes the US and the UK -- will need to do a test, while the unvaccinated will be allowed in only for essential purposes. United Airlines will resume nonstop flights from Washington Dulles Airport to Paris Charles De Gaulle on July 1.

Denmark has also opened to fully vaccinated travelers from the UK and the US and its neighbor Norway is letting the fully vaccinated skip quarantine.

All foreign tourists can now visit Greece without the need for quarantine on arrival, provided they have a negative PCR test. The government plans to declare 80 islands -- including most of the country's top tourism destinations -- Covid-safe by the end of June.

The island of Cyprus is open to vaccinated travelers from 65 countries, including the US and the UK.

Slovenia has also reopened to tourism with its own traffic light system and testing requirements, which you can read about here.

The Netherlands is welcoming tourists from "safe countries with a low Covid-19 risk," while Iceland, a member state of the European Economic Area, opened its borders to vaccinated travelers back in April.

Croatia is also welcoming vaccinated travelers, as well as those who present a negative PCR test or proof that they've recovered from Covid-19 within the past 180 days, and no less than 11 days before they arrive.

The UK's transport minister, Grant Shapps, announced via Twitter on June 9 that a US-UK taskforce had been set up to facilitate the reopening of transatlantic travel, but there is no news yet of resumption of flights.

The Isle of Man, a self-governing British Crown dependency in the Irish Sea, is reportedly on course to fully reopen its borders with the UK on June 28, having been closed to almost all non-residents since March 2020.

Having recently been knocked off the UK's green list, Portugal is hoping to build up some tourist numbers by welcoming vaccinated US travelers, but no date has been confirmed yet.

The Americas

The Macy's July 4 Fireworks -- pictured here in 2020 -- will be open to in-person viewing this year.

California is poised for its grand reopening of business on June 15, with masks becoming optional in many public settings -- although restrictions vary between the vaccinated and unvaccinated. Be sure to check ahead before traveling, as there will be plenty of caveats.

New York City will be following suit on July 1 and, to kick the month off on style, Macy's July 4 Fireworks will return to being an in-person event.

Canada, which has only been open to essential travel since the pandemic began last year, has given a cautious nod to possibly allowing fully vaccinated citizens to return home as early as July.

The Caribbean island of St. Bart's is now welcoming fully vaccinated travelers from the US while UK and EU residents just need to do a pre-departure Covid test. St. Lucia has also eased on-island protocols for vaccinated travelers -- including being able to book rental cars and dine at more local restaurants.

Middle East, Africa and Asia

Morocco will reopen to international travelers on June 15 and Algeria is also starting to reopen air travel. In the United Arab Emirates, Abu Dhabi will end mandatory quarantine for international travelers on July 1. That's the same day Phuket will be reopening over in Thailand.

Covid escape plan of the week

The UK's green list of countries its citizens are allowed to travel to is "select," to say the least -- there are only 11 destinations and some are so remote they only recently acquired an airport.

However, there is some good news for fans of sheep-strewn archipelagos. Atlantic Airways is starting direct flights from Edinburgh to the Faroe Islands on July 1 -- although at £308 ($406) per person return, it's not cheap for a short hop.

The islands feature in the hotly anticipated and long delayed James Bond movie "No Time to Die," coming later this year, and a new Sightseeing Tour visits the key locations. Keep your eyes closed to avoid spoilers.