Balancing sound levels is the first thing you do with your sound.
The sound on a track should be balanced so that the sound level is even. Its average should reach -11 to -9 dB. Peaks should not reach higher than -5 dB.
Using keyframes you can lower (or rise) sound level section of a clip.
Limiter cuts off sound level peaks. Should be used moderately to balance sound levels.
Compressor, lowers high sound levels and raises low levels.