From September 9 at 11am PT/2pm ET to September 12 at 4pm PT/7pm ET, Blizzard will be hosting an Overwatch Free Weekend on PlayStation 4 and Xbox One.
This will allow anyone to play on all 13 maps with all 22 heroes in a variety of modes, though Competitive Play wont be available during the weekend.
PlayStation Plus isnt required on PS4, but Xbox Live Gold is required on Xbox One