The sub as a whole is for "daily games", a genre that's existed in some form for decades (such as the daily crosswords in newspapers) but really became popular online starting with Wordle a few years ago. A new puzzle in the same basic format every day.
This specific post is about a game called Connections, where you're presented with 16 words/short phrases and have to group them into 4 groups of 4 based around a single connection. Often there will be distractor connections with 2, 3, or even 4 words that could fit into a category, but if you used that category it would be impossible to group the remaining 12 into three groups of 4. Or there may be 5 or 6 possible words in a correct category, in which case you must find which one(s) need to go in a different category in order to complete the puzzle as a whole.
There's also Categories and Conlextions which do exactly the same thing, if you want to play more of the same game, or you don't want to use a product by the New York Times (who publish Connections).
Easy street is a pretty old term in the US. I don't think I have heard it commonly used since the 90s. It basically means you're set financially, you don't have to work for it.
Easy listening is like Frank Sinatra, Tony Bennet, Nat King Cole.
An easy chair is big and comfy, and usually soft and fluffy.
I think all of these terms are older, and not really used much now. Well, except for easy money.