Noise gate is a mono noise gate, mainly designed for guitar.
Use it for audio noise reduction before or after applying other VST effects that may highly amplify noise like a distortion, compressor (sustainer, limiter) or a guitar amplifier at high gain.
This plugin can also make noise reduction on a whole phonogram with some conditions. But the main purpose is to cancel noise from a microphone or pickup of a music instrument like guitar before other sound processors. It has good enough characteristic at signal release.