Demo

A demo is a client- or serverside recorded replay. Demos are used in competitive play to prove the correctness of a played match and for creating fragmovies. Since demo files are really small, it's easy to share whole matches with other people which would be huge files when saved to an actual video format.

Recording Demos

To record a demo you need to type in g_synchronousclients 1, record [nameofthedemo] and after that g_synchronousclients 0 into the console (without the []). Some mods allow recording demos without having to type g_synchonousclients everytime.

Watching Demos

You can watch demos by either opening the demo menu or by typing in 'demo [nameofthedemo]' into the console (without the []). The demos need to be in the base/demos folder to get recognized by the game.

Files Types

Jedi Academy on version 1.0 reads .dm_25 files while the update 1.01 uses .dm_26 files. Jedi Outcast uses dm_15 (on version 1.02 and 1.03) and dm_16 files.

Software Demos

The term 'demo' may also refer to a freely distributed piece of an upcoming or recently released video game. Demos are typically released by the game's publisher to help consumers get a feel of the game before deciding whether to buy the full version. (Source)