is there documentation from oracle explaining the difference between 'Name' 'Customer' and 'Entity' fields? as in when the user should use each one and in which contexts?

It's a bit tricky since you're really talking about three different things (or more), i.e. how it shows up in the UI, how it shows up on saved searches, and what the table structure actually looks like. The tl;dr is that they're kind of all the same field on the backend, but named differently and filtered b/c JE lines can be associated with customers, vendors, or employees as you could have a payables or receivable line. Whereas customer/vendor is used on transactions that are specifically restricted said relationship type like a (customer) invoice or vendor bill. The best source of documentation is probably the SuiteScript Records Browser (just search for that in SuiteAnswers and you'll find a link to it), which will at least tell you the native field UI lables and internal IDs, but still might not help you 100% in terms of saved searches. But at least there you can sort of compare the generic "transaction" to the specific transaction type (e.g. "Journal Entry") to get a sense of what's there. Note that many of those fields all share the same internal ID {entity} so that's kind of the catch-all, whereas the others are more restrictive to specific sets of transaction types.

records browser has not been super helpful specifically for saved searches/saved reports crying sunglasses i was hoping there was something available to explain to users why sometimes the field name they were looking for doesn't show up on the dropdown menu, or why the same field has a different label in different parts of netsuite. i just don't know how to explain it lol

Yeah, it is fairly painful. I don't there's a real explanation other than just technical debt built up over time at NetSuite/Oracle. But hey, someone's gotta help keep us admins employed. 😆