This may seem like a basic question, but I’ve never really understood the role of a solenoid valve in pneumatics; I couldn’t understand the definitions. So, what do they do and how do they work?
Theres tons of info that can be found here
Real talk though - there are a ton of threads (old and new) that answer a lot of the technical questions you’re asking. Search around a bit, stumble through a few old threads - you’ll be pretty amazed at whats buried in this site.
For the purpose of FRC, solenoid valves are what open and close the pathways for the pressurized air to move the pneumatic cylinders. When a solenoid valve is in one position, the air pressure flows into one port and causes the piston to extend. When the solenoid valve is the other position, the air pressure flows into the other port and causes the piston to retract.
This link can be pretty helpful:
Strictly speaking, the valve directs air. The solenoid is the coil of wire & metal piece that moves in response to electric current that actuates the valve.