Here's an excerpt:
The word “station” comes from the Latin word statio, meaning a soldier’s post. On special days the faithful of Rome, together with the Pope, would gather at a particular church (the ecclesia collecta) and then solemnly proceed to the statio, the church chosen to be the “post” where Mass would be offered. During the procession a litany would be sung or a psalm (which would later become the Introit of the Mass). Once there, the pope would “collect” the people and their petitions into a single prayer—the “collect”—and then begin the Mass.
