Mycelium culture techniques allow cultivators to grow mushroom mycelium on a variety of liquid mediums. The mycelium can then be used to colonize spawn much more quickly than with spores.
Too lazy to bother trying to get the mushrooms to fruit? This document tells you how to grow and trip off the mycelium. It's definitely easier, but you yield a much lower quantity of psychoactive material.
The achievement of this tek is to shorten the time needed to colonize a jar as you'll see signs of growth in 24/36 hours, instead waiting 3/5 days for spore germination.