TheWavMan recaps the four core compression parameters using a single, memorable analogy: a parent telling you to turn down your music. Threshold is the volume level they're willing to tolerate. Ratio is how much you turn it down once they start shouting.
Attack is how fast you respond to that shout, and release is how fast you crank it back up after they leave the room. Each parameter maps to a concrete, physical action, which makes the relationships between them easier to hold in your head when you're actually dialing in a compressor.