How do Hydraulic Control Valves

/ How do Hydraulic Control Valves #12  
Thanks for the illustrations RCH. It reinforced the schematic I had visulized from the description.
 
/ How do Hydraulic Control Valves #13  
Referring to the diagram that uhmgawa posted. Does this circuit work like this. When the valves are operated, the return oil from the cylinders gets dumped to the return line, and there is no pressure in the power beyond line? The diagram notes that there is only pressure at the second valve when both the valves in the first unit are in neutral.

Also what do the terms "spool" and "valve" mean in hydraulics? Is the valve the hunk of metal that the lines connect to, and the spools are the controls that direct fluid to the piston/motor/whatever?

Looking at the diagram of the valve assembly behind the levers there is a round doohickey that is labled "spool attachment". Is this just the place to bolt this unit to something, or is it something else?
 

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