The first three are generally used to control twin-coil switch machines, that require MOMENTARY electric charges to actuate. (Connecting for more than a second or so will cause the coils in the switch machines to overheat/burn out.) Instructions should be on the back of each package. The red buttons on each are momentary switches. They may be actuated by pushing down on them. I haven't really used them, as I prefer toggle switches mounted on my control panels, but the functions are the same.
The Snap-Relay is a twin-coil device, similar to the Atlas switch machines, but without the throw bar. The Snap-Relay is useful for several things: it can be used to reverse the track polarity for reversing loops, wyes, and for changing the aspects (lights) on signals. I use them, wired in parallel with twin-coil switch machines to show on the trackside and/or control panel signals, which route the train will take. Again, the actuating current for the Relays is momentary.