https://www.gamespot.com/articles/new-overwatch-update-makes-post-matches-friendlier/1100-6460040/

The new version 1.25 update for Overwatch makes matches a friendlier place, along with a spate of balance changes and other tweaks. The biggest change comes in the form of Endorsements, a tool you can use after a match to recognize fellow players for their good teamwork, sportsmanship, and shot-calling. You can also endorse players from the opposing team for sportsmanship.

The incentives to embrace the endorsement system work both ways. Endorsing other players gets you bonus XP, and the more endorsements you get from other players, the higher your Endorsement Level will rise. You can get up to level 5, and claim rewards based on your level.