From the developer's web site:
[WordHero] is a highly addictive word puzzle game. Everyone plays the same board at the same time. At the end of the round, you are shown your score ranked against everyone else. Players score points by tracing their fingers over letters to make valid words on a 4×4 grid.
Track your highest scores against everyone else hourly, by day, week or month.
Each tile can be used in at least two words and you can earn bonus points for using every tile adding an additional element of strategy.