As Gary said SCV stands for Selective Control Valve. Each valve is made up of a valve body (which the hoses attach to) and a moveable internal "spool". When you move the control lever the spool moves inside the body and changes the amount and direction of hydraulic fluid flow. There are two basic types of spools- "single acting" and "double acting". A single acting spool has one input and one output and moving the spool changes the amount of fluid through the spool. A single-acting spool can only drive a cylinder one way. A double acting spool has one input and two outputs. Moving the spool not only changes how much fluid flows but also which output it goes to. Thus, a double acting spool can drive a cylinder in both direction. Pretty much all of the valves on a tractor are double acting. If you want to control more than one motion then you just parallel more valves (and spools). Your loader has two spools- one for up-down and one for tilt. A 5 spool SCV could control 5 motions.
Dave