what3wordsVerified account

Good explanation on their site. We used it during a race and it was great. https://what3words.com/about-us/ 

Yes but how the heck do you know which 3 words to use. And how did the 3 words above come to pin point them? That's not explained

Or is it the case that you must have the app installed in order to find the 3 words? If that's the case why not just use GPS which every modern phone comes with anyway

I’m assuming the folk used what3words for their location and relayed that to the rescuers. Then they can pin point that area and go get them, unless there is another feature for rescue teams we don’t know about. They have mapped out the world using three words at a time.

Yep. But I think the issue is these guys were totally unprepared. The rescue guys had to ask them to download the app. I'm struggling to see why GPS couldn't have worked

Possibly language barrier issue

I guess. But not a great barrier if they were able to direct them to download the app.

Rescue teams use OS grid references for navigation. They can get one from a Three Words reference, but it's just an extra step. I have a free app that gives me a grid ref straight off - OS Locate. No faffing.