Passenger
Passenger is a job without a specific department.
Passengers are crew members with no explicit duties on the station. As such, they generally may roam around public areas of the station at their leisure, though officially speaking they're also subordinates to all other crew members. Passengers are uniquely one of the only roles that have an infinite number of openings, so the role is always available.
The lack of pressing responsibilities makes this role a good choice for newer players who want to grow accustomed to basic gameplay without the pressure of working a specific job. Some experienced players also enjoy this role, as the lack of important duties allows them to spend their time pursuing personal projects or interacting with other crew members. Antagonist passengers benefit from having a good excuse to be wandering around odd places instead of doing actual work, though they also lack easy access to the specialized equipment that can be found in proper workspaces.
Due to the grey jumpsuits that passengers start with by default, as well as the unlimited number of job openings available, Passengers are commonly nicknamed "greytiders" by other players (among a few other variations such as "the tide", "greyshirts", and "the greys").
Getting Promoted
While a Passenger's lack of responsibility provides them with freedom, it can also be somewhat dull, especially during longer shifts. Additionally, sometimes a department may be understaffed and need eager hands to help the station run properly. In cases like these, you may ask to be assigned a proper job to occupy your free time.
The Head of Personnel has the authority to alter the job title and access permissions on your ID card, which you'll generally need done in order to properly work in a new department. In most cases, an ID change will likely need both the Head of Personnel's approval and the approval of the head of the department you want to join (typically via a stamped form).
Aside from being formally reassigned to a new job, you might also decide to remain a Passenger and just run odd jobs for other departments (such as helping Cargo deliver mail, helping Science find anomalies, or helping the Bartender rearrange the bar's furniture).