Specific to recording, plug-ins are software (programs/scripts) that can be used in conjunction with various recording/mixing software. Typically, they are in the form of effects (reverbs, delays, compression, etc.) or virtual instruments (synthesizer sounds, etc.). VST stands for Virtual Studio Technology, and is a plug-in format developed by Steinberg for use with Cubase products (although many other popular recording programs support VST plugs). The designation VSTi is usually used for virtual instruments in the VST format. Direct X is another common plug-in format for recording.