Both Golems and Golemites do splash damage, similar to Balloons, when destroyed.
Golemites prioritize defensive structures above all other targets, and will bypass all other types of enemy buildings and troops while any defenses remain on the battlefield. This is true even if they are under attack by enemy Clan Castletroops, heroes or Skeleton Trap skeletons. Note that like all troops that prioritize defenses, Golemites do not consider the Clan Castle to be a defense regardless of whether or not it contains enemy troops, but do consider the defending Grand Warden to be a defensive building. Once all defenses are destroyed, Golemites become like any other troop with no preferred target; they will attack the nearest building to them regardless of type, and will turn and attack enemy units if they become aware of any nearby.
You cannot train or place down Golemites, as they only appear when a Golem dies.