There are 3 main different technologies; Direct acting, In-direct acting and Forced-lift piston type.
Direct-acting valves require no differential pressure to remain in their rest state and in the NC version, they will only allow flow once energized. These valves are very robust and can be used in a process line for simple isolation purposes of for safety purposes. The can also be used on the outlet to a tank where sometimes pressure can get very low but the valve needs to remain open.
In-direct acting valves require a pressure differential across the inlet and outlet to allow them to stay in their rest state. For example if a valve was normally open and there was not a large enough pressure differential, the valve could be intermittent and possibly close if inlet pressure dropped too low. These valves should only be used if pressure levels are within the parameters specified in the datasheet and IOM instructions.
Forced-lift valves are used in high pressure applications where neither of the above valve types can deal with the higher pressure processes such as 40 Bar plus. This valve uses a much bigger and higher power coil to open or close and the seat of the valve is directly connected to the bottom of the piston/plunger assembly eliminating the need for a diaphragm.