Secret Agents or Agent Secrets?

Here are some questions that ought to be relevant to a number of us.

Is an "agent" ALWAYS something that acts on something else?

Or can an "agent" do actions without an object, like "jump" and "skip?"

If the answer to the last one is "no," then what do we call the jumper or
skipper?   I've heard the term "mover" used, but what about verbs that stand
for things voluntarily done that don't necessarily involve movement like
"meditate?"

In languages that don't need reflexive pronoun, what name do we give the
subject's semantic role?    (I don't think they're called "atients" or
"pagents.")

What do we call the semantic role of the subject in a clause with reciprocal
voice in a language that needs no reciprocal pronoun?

Where can I find good laymen's definitions of case grammar terms?

Thanks in advance to all who answer,

Jim