So I thought I knew what those terms meant, but I'm rather new to all this and thought I should clarify. Are these terms used to determine whether you have submitted to multiple agents in ONE agency (vs one agent in one agency), or are they used to state whether you have submitted to multiple agents in multiple agencies (or one agent per multiple agencies)? Does that make sense? I thought it was the latter, but recently realized I might be wrong. Any clarification is appreciated, thank you!
An exclusive means you won't send the manuscript to any other agent for the duration agreed (I think exclusives are a bad idea in general, but if you agree to one then make sure there's a sensible time limit). Simultaneous submissions generally refers to submissions to other agencies, because I don't think any agency allows you to query multiple agents within their agency at the same time. The only thing to watch out for is for some agencies, no from one means a no from all - once you have a rejection from one agent there, you can't query any others. If this is the case, they will state it in their submission guidelines. If not, you can query another agent at that agency once you get a rejection. Hope that helps!