A Session is a singular gaming event that usually runs between 3 and 6 hours, and consists of 1 or more players and a Game Master. Typically food and drinks are enjoyed while players sit around a table with each other and engage in social role-playing, each player having taken on a player character who they improvise and act as with the others at the table.
A session can contain countless things, but typically every session contains at least one round of combat. Some sessions may be heavy in combat, but others emphasize political intrigue, stealth, or even puzzle solving.
The in-game location of a session is typically dependent on the players, their characters, and (if the session is part of a campaign) the events of the previous sessions.