What is plugin rescan?
The action that makes a DAW re-read its plugin folders and pick up newly installed items. Hosts scan at startup and on demand, so a plugin installed while the DAW was open will not appear until a rescan.
Hosts also keep a blocklist of plugins that failed a scan. If an install was interrupted, clearing that list is often the missing step.
The third-generation Virtual Studio Technology plugin format created by Steinberg. It is the standard way third-party instruments, effects and utilities load inside a DAW on Windows and macOS, using one shared plugin folder per system.
A digital audio workstation: the software you record, edit and mix in. Cubase, Logic Pro, Ableton Live, Pro Tools, FL Studio, Studio One, Reaper and Cakewalk are the ones most vocal sessions run on.