There's other forms of parallel compression that you can dig into.
But with parallel compression, you're blending the input signal with the same input signal but heavily compressed.
Not to sure how the glue operates, but given a fundamental understanding of the dry/wet settings, i think it achieves the same result so to speak.
obviously biasing the dry/wet setting to one particular in it's entirety, will remove the parallel affect.
Looking to the word parallel, will also help you understand the idea of this technique a little more.