The two slots, which are opposite but parallel to each other, are on the edge of the pump head. When the pump goes forward, the O-ring is forced into the back of its groove by friction, which creates a seal. Then the pump is pulled out, that same friction causes the O-ring to be moved to the front of its groove. This uncovers a hole in the back that allows air to travel under the O-ring and through the twin slots into the pump chamber. That's why it's important to keep them free of glue or other blocking agents.
Thanks for clearing that up for me SHA, thats what I ment by "air intake valve", I just didn't know where it was. I didn't realise it was part of the plunger head.
So, wait...the springy things do nothing?
The springs/wires that are inside or on the outside of pipes are there to stop the pipes from bending, for example, if you bent the pipe at a right angle the pipe would propbably close up and let little to no air though. They are also there to protect them from breaking. This is mainly for when the gun is assabled at a factory, so they can be assambled more quickly without the risk of pipe damage. They're mainly at places where the pipe could bend the most, or be most likely damaged.