Yeah, it’s as Malciks says.
Crusader Strike is an ability common to all Paladin specs.
At some level (I don’t know which), Retribution spec gets a passive trait called Improved Crusader Strike, which gives the ability two charges (Holy only ever gets one charge, except when using Avenging Crusader; Protection only gets one charge, but all Protection Paladins talent into another ability that replaces Crusader Strike entirely with one of two new abilities)
Additionally, midway down their talent tree, Retribution Paladins can select a choice node to get either “Crusading Strikes” (which removes Crusader Strike from their bar, and improves their auto-attack damage, while allowing every other auto-attack to generate Holy Power) or “Templar Strikes” (which retains the two charges of Crusader Strike, but makes the second one do more damage, and changes their damage type to Radiant instead of Physical)