The Session is the fundamental document type that is created and modified by the Ardour workstation. A Session is a folder on a computer filesystem that contains all the items that pertain to a particular project or "recording/editing/mixing session".

The Session folder includes these files and folders:

• session_name.ardour the main session snapshot
• *.ardour, any additional snapshots
• session_name.ardour.bak, the auto-backup snapshot
• session_name.history, the undo history for the session
• instant.xml, which records the last-used zoom scale and other metadata
• interchange/, a folder which holds the raw audio and MIDI files (whether imported or recorded)
• export/, a folder which contains any files created by the Session > Export function
• peaks/, a folder which contains waveform renderings of all audio files in the session
• analysis/, a folder which contains transient and pitch information of each audio file that has been analysed
• dead sounds/, a folder which contains sound files which Ardour has detected are no longer used in the session (during a Session > Clean-up > Clean-up Unused Sources operation, will be purged by Flush Waste Basket, see Cleaning Up Sessions)

A session combines some setup information (such as audio and MIDI routing, musical tempo & meter, timecode synchronization, etc.) with one or more Tracks and Buses, and all the Regions and Plug-Ins they contain.