crankshaft counterweights

OK, you smart people, just some curiosity questions:

There appears to be some lack of precision in terminology, where the term
"crankshaft counterweights" sometimes refers to the big weighty parts of the
crankshaft that are part of the single piece of metal, and other times refers to
some movable parts that are attached to the crankshaft. Am I right about this
lack of precision?

Is there a simple way to tell, say from the engine model number, whether an
engine is equipped with the movable type of crankshaft counterweights?

How are the movable type of crankshaft counterweights attached to the
crankshaft? Does anyone have a picture or drawing or explanation?

When an engine is equipped with movable counterweights, is there one per
crankshaft journal, or just one or two per crankshaft, or what? If not one per
journal, where are they placed?

In what plane (in the geometric sense) do the movable counterweights move? I
assume they are free to move in a plane perpendicular to the axis of crankshaft
rotation, is that correct?

How free are the movable counterweights? Is there an angular limit to their
motion, or do they rotate through a full 360 degrees (with respect to their
attachment point), or what?

How massive are the movable counterweights, typically?

What is the physics of the operation of the movable counterweights? How does
their presence reduce torsional vibration?

Thanks.

Dave