Overwatch, Blizzard's attempt to diversify the MOBA genre, will soon be playable by a select number of people in the upcoming closed beta, which begins on October 27.
Blizzard will allow a small group of testers regular access to Overwatch, and hopes to add more to the list as more features become available for testing. Blizzard is requesting a lot of feedback from these testers; asking them to dissect every hero, map, and ability in the Beta forums.
Blizzard will also be inviting more people to play on "Beta Test Weekends" in which Blizzard hopes to push Overwatch's servers to the limit. The first "Beta Test Weekend" is scheduled for sometime after Blizzcon, which is on November 6 and 7. These weekends limit the heroes, maps, and gameplay modes available since it is primarily tech focused.