There are three types of Plugins in Zrythm.
Instruments are Plugins that are used to generate sound, such as synths or pianos.
Effects are Plugins that change the audio signal passed to them. Examples are Reverb, Chorus and Flanger.
Modulators are used to modulate the parameters of other Plugins. These include LFOs and envelopes.
Zrythm supports LV2 Plugins at the moment.