MusicTechHelpGuy breaks down what compression actually does: unlike EQ, which shapes frequency, a compressor shapes dynamics, evening out the gap between a track's loudest and softest moments over time.
He demos this on a lead vocal in Logic Pro, playing it bypassed and then compressed so you can hear the difference directly. Watching the gain reduction meter (up to 10 dB on louder phrases) shows exactly when and how hard the compressor is working.
The goal on vocals is intelligibility and consistency, making sure every word sits clearly in the mix rather than getting buried or jumping out.
He also notes that compression isn't one-size-fits-all. On percussive sources like kick and snare, the same tool gets used differently, shaping transients to add punch instead of leveling out dynamics.