History of Subclass

A subclass is an elemental specialization of a Guardian class (Titan, Hunter, Warlock); subclasses can be switched at any time. The elements are Solar, Void, Arc, Stasis and Strand, plus the multi-element Prismatic. For Titans these are Sunbreaker (Solar), Sentinel (Void), Striker (Arc), Behemoth (Stasis) and Berserker (Strand).

The source does not detail how aspects and fragments work; see the individual subclass pages.