VST plugins
There are three types of VST plugins.
VST instruments generate audio. They are generally either virtual synthesizers or samplers. Many recreate the look and sound of famous hardware synthesizers. Better known VST instruments include Massive, FM8, Absynth, Sylenth, Reaktor, and Omnisphere.
VST effects process rather than generate audio—and perform the same functions as hardware audio processors such as reverbs and phasers. Other monitoring effects provide visual feedback of the input signal without processing the audio. Most hosts allow multiple effects to be chained. Audio monitoring devices such as spectrum analyzers and meters represent audio characteristics (frequency distribution, amplitude, etc.) visually.
VST MIDI effects process MIDI messages (for example, transpose or arpeggiate) and route the MIDI data to other VST instruments or to hardware devices.
What is a VST or VSTI audio plugin ?
VST stands for Virtual Studio Technology and is an interface for integrating audio synths and effects plugins with your digital audio workstation (DAW). In plain English you could simply say its a way to get all those cool hardware effects racks, keyboards and drum machines into your choice of music software such as Cubase, FL Studio or Logic Pro etc.
Virtual Studio Technology
Virtual Studio Technology (engl. für virtuelle Studiotechnologie), kurz VST, ist der Markenname eines Software-Protokolls für die Musik- und Tonproduktion. Entwickelt hat VST das Unternehmen Steinberg Media Technologies ursprünglich für sein Sequenzer-Programm Cubase im Jahr 1996. Es etablierte sich einige Jahre später als Industriestandard. Wenn ein Entwickler ein Plug-in für ein großes Audioprogramm herstellt, stattet er es typischerweise mit dem VST-Protokoll aus.