Editing & Post-Production
Media cache
Also called: cache files, peak files, conformed audio
Open a project and the software analyses every clip, writing audio waveforms, conformed audio and index files somewhere on disk. Playback and scrubbing then read from those instead of decoding the original each time. Delete them and they rebuild themselves.
The problem is that they pile up, project after project, and a full system drive is the most common reason an edit turns mysteriously slow. Point the cache at a fast drive away from your system disk, set a size or age limit in preferences, and clear it when a project is archived. Nothing you have edited lives in there, so clearing it cannot lose work.