A session is something your group runs at a set time: a shift, a training, an event. Sessions have a type (which decides the roles in them), a host, and slots that staff can claim.
The pieces
Session type: a template such as "Shift" or "Training". It decides what roles exist in the session (Host, Co-Host, Trainer and so on) and its statuses. See "Session types, roles and slots (set-up for admins)".
Session: one occurrence of a type at a date and time. A session can be a one-off, or part of a repeating schedule ("Wednesdays at 18:00").
Roles and slots: each role is a place that one or more people can take. Taking a place is called claiming.
Host: the person running it. A role marked as the primary host makes someone the host.
Tags: labels you can put on a session to say what kind of training it is (for example Security or Management).
Where you see sessions
The Sessions page shows a schedule by day. There is a My Sessions option to show only sessions you host or take part in.
Your Home page shows the sessions you have claimed for today, with a LIVE marker for one that is running.
The iPhone and Android apps show them too.
You can add them to Discord as events, and subscribe to them in your own calendar (see "Sessions in Discord: reminders and Discord events" and "Add Rosterr sessions to your calendar (Google, Apple, Outlook)").
How they connect to everything else
Activity: hosting, attending and logging sessions count towards quotas and goals ("Sessions hosted", "Sessions attended", "Sessions logged"). See "Quotas explained (types, who they apply to, and how they are completed)".
Leave: when a leave request is approved, Rosterr takes that person off any sessions inside their leave. See "How do I request time off? (inactivity notices)".
Moderation and Alliances can also use sessions as part of their work.
Seeing sessions needs permission
Each kind of session (Shift, Training, Event, Other) has its own permissions: see, claim, assign, create, manage, notes, tags and edit concluded. If you cannot see a kind of session, your role lacks "See ... sessions" for it. See "Session permissions explained (what each one lets someone do)".
Related articles
Claim a place in a session (and assign others)
How do I create a session? (one-off and repeating)
Session types, roles and slots (set-up for admins)