What does RB1 mean on a depth chart?

RB1 means the first running back listed on a team's depth chart. The designation usually identifies the player expected to start or handle the leading role when healthy.

RB1 does not guarantee every carry or snap. NFL teams commonly divide rushing, receiving, pass-protection, and short-yardage work among several backs. In fantasy football, RB1 can also mean a running back ranked among the top starters rather than a specific team's starter.