Same thing but instead of pressing a button you initiate a movement with a thumb.Spring is weaker on the assisted knives and deployment is smoother as opposed to a snap in the automatics. In the end it is kinda the same thing but automatic can be little faster.

Also there is another way to get a knife to be open everytime you draw it out. I saw some of the Emerson knives to have a pocket clip when you thumb stud is. When you draw the knife out, blade is anchored to your pants and unfolds so when you pull it out it is fully deployed. Freaks me out a bit.