Aviation Snips is another name for compound action hand snips.
Blades are hardened in order to provide sharp and long lasting cutting edges. This process tends to make them brittle and twisting can have the effect of chipping or breaking them.
Compound Action
This provides additional power through the use of a double fulcrum.
Plain Snips
These are similar to a pair of scissors. They can be opened and closed by hand.
Spring Action
Incorporating a spring so that the blades will open of their own accord.