Automatic is a knife that has a spring inside that when certain release mechanics (usualy a button) is pressed the blade opens. There are two types of automatic knives:
1)otf - OUT THE FRONT which means that blade slides out of the handle. Advantages: more secure grip when knife is opening and knife is usually smaller. Disadvantages: older models required a hard surface to cock the knife back into place, this combination is not so great for stabbing/poking

2) side openers - which means that blade swings out like on the regular knife. Advantages: more secure locking mechanism makes this as good as any manual folder, some models can be used in manual mode Disadvantages: wrong hand position prevents deployment.


In any of the above combination accidental deployment is something to worry about. Obviously side openers are little bit less dangerous that OTF if accidental fireing happens.