What the hell is "endorsing"

So I was feeling overwatch yesterday and decided to jump into a quick play match cus why not? I ended up seeing this blank 1 at the top right and had no clue what it was, and neither did any of my teammates. After playing the game I got 3 "endorsements" 2 for being a good teammates and one for playing well.

So what are these supposed to do exactly. I think I get why you would endorse someone, but I don't get the purpose for it.

(Also someone who seemed to have a lot of endorsements was really toxic and kept yelling at me when I killed them, calling me shit for flanking when they didn't check their flanks. So..)