Known by several names such as "the tide", "greyshirts", "the greys", and several more colorful ones, passengers have no explicit purpose or responsibility on the station. As such, this is the most newbie friendly role in the game, allowing you to get acquainted with the controls and the various tools around the station without causing a massive catastrophe (hopefully). On the other hand, experienced players can use this role as a way to move around as they please without being tied down by assigned duties.
This freedom makes them avid troublemakers, as their lack of any meaningful starting equipment makes stealing very inticing. They also enjoy hoarding any tools they find for completely legal and helpful activities. This leads to an uneasy distrust of most passengers by default, however most crew will be receptive if you just act like a normal human being and not like you'll steal their bag at first chance.
Jack of all, master of none
Passengers can be the most versatile characters in the game, the only things stopping you being game knowledge and means of getting around. Go to the arcade and play tetris all round. Get bored and go play the bar piano. Find some hacking tools and snoop around the station for goodies. Get chased by security for trespassing and give the Lawyer a reason to exist. Get bailed and immediately harass Head of Security for more station access. Get a job at the local botany instead.
Just because you answer to everyone, it doesn't mean you're playing Slave Station 14
unless you're into that. What it means is that everyone has more authority when telling you to cut it out. If you see a Clown preparing a prank or a Mime starting a performance and decide to bother them, they have the right to pull rank on you and tell (or gesticulate at) you to GET OFF THE STAGE YOU ABSOLUTE AMATEUR.