In X-Men: Destiny, players are put in the role of new mutants who join the X-Men or the Brotherhood of Mutants; they have to make choices to decide the ultimate destiny of their character. X-Men: Destiny places an emphasis on "choice", as opposed to a more traditional linear type of gameplay. According to the official press release, "the all-new original video game casts players as new mutant recruits in a rich, branching storyline that features a deep element of choice and gives players ultimate control of their destiny".
Throughout the game, players collect power enhancements called "X-Genes." Every X-Gene can unlock three types of abilities: offensive, defensive, and utility. X-Genes can be mixed and matched as the player sees fit for a unique experience.
Source: Wikipedia, "X-Men: Destiny", available under the CC-BY-SA License.