When renting a car in Oregon, does the agent have to explain to me what insurance options I am accepting/declining?
There are two separate questions that you would be interested in. One is whether you understand the terms of the contract: you probably don't, but also, the agent probably doesn't either, and they cannot give you legal advice about what the contract means. So you have to take it or leave it (and typically one takes it).
The other is whether you actually have been told what the terms are. The answer usually is "No, not really". The document that you sign / initial does not contain all of the terms of the contract, but will (or should) refer to some other thing that constitutes the full set of conditions – let's call that the "external specification" (I don't know of a uniform name for the thing). You can request a copy of that thing, or ask to see it, but they may not be able to provide it to you at the counter (I had that experience in an airport). You choice they is simple: if you do not have faith in the company spelling out the terms of the contract in honest legalese, you should not sign the agreement. Otherwise, you might reasonably do so. Certain concepts usually are left open, such as "administrative fee".
It's generally up to you to inform yourself of the terms of any contract you are entering - the other party to the contract is not obliged to do it for you.