With the exception of the end of Vayigash, every Sidrah (Shabbat weekly Torah reading) ends at a parsha (paragraph end.)
When there is a parsha end in the middle of the sidrah, Chumashim use a single ס or פ. At the end of the sidrah, most Chumashim use 3 ס or פ. (See an example here.)
Why do they use more than one, and why specifically 3 (as opposed to 2 or 4, etc.)?