Really great multiplayer game.
I have been playing Overwatch basically since it came out (I think I bought it a month after release) and have seen all the changes it has undergone. It is a team-based shooter with 30ish different heroes to choose from.
Each hero is unique with their own weapon, special abilities, and ultimate ability. There are 3 basic roles for the heroes: tank (big; take damage for team), damage (squishy; kill the other team), and support (squishiest; heal your team).
Best part about this game is how it has evolved over time and will continue to do so. The developers do not always make fixes to overpowered characters as fast as the community would like, but they do make them. A steady stream of new maps and heroes keeps the game fresh.
One bit of advice: try to find a group to play with even it is just one other person. It will make matchmaking sooooooo much better.