Here we have a 4 way 3 position valve shown in the centre position. This means it has four pipe connections to the valves but 3 different switched positions possible.
Note how this valve now has two springs instead of one. With no signal to the valve, it will sit in its central position blocking flow to all ports.
When the electrical solenoids are operated the spool position moves to either the right or left-hand position.
The second symbol shows a 2 position detented valve. This valve has no springs but instead, the spool is held in position by a mechanical detent when electrical power is removed.
Finally, the third symbol shows another 4 way 3 position valve but with a different centre position layout. In this valve, the A and B lines are connected to tank instead of blocked, as shown above.