Zimple-Gate is a noise remover plug-in.
A noise gate is generally used to remove unwanted noise or sounds from a recorded audio track. To operate the gate, you have to first set the Threshold level; any sounds on the track that have a an amplitude level below this threshold will be muted. Think about this as an actual gate that will close in front of any sound that is below this threshold and open for sounds louder than the threshold.
In addition, you will have to set the Release and Attack time. The Release determines how fast the gate will close once it detects sounds below the threshold, while the Attack determines how fast the gate will open once it detects louder sounds. Depending on the nature of the sound (more transient or with a smoother envelope), different Attack and and Release settings will be necessary to obtain a natural result; even an infinitesimal difference in the settings can make a noticeable difference on the sound.