Plugin host
The program that loads audio plugins, feeds them audio buffers and shows their interfaces — usually a DAW, sometimes a standalone tool.
A VST or CLAP plugin is a shared library with no main loop of its own. The host calls its process function on the audio thread once per buffer, passes in automation and MIDI, reports latency for delay compensation and saves the plugin's state in the project file. Standalone hosts such as Carla or Plogue Bidule exist for anyone who wants to run effects live without a full DAW.
Traditionally plugins run inside the host's own process, so one crashing plugin takes the whole session down with it. Bitwig Studio launched in 2014 with sandboxed plugins in separate processes, and AUv3 builds the same separation into the format itself. The price is a little overhead per call — which most people consider cheap next to a lost take.