My Anchor program spits out an error that looks like: custom program error 0xa2. What does this mean? Where can I learn what this error means?
This is Error: 162: 8 byte discriminator did not match what was expected.
That means anchor was expecting an account's data to start with a certain 8 bytes, but it didn't.
That could be because you passed in the wrong kind of account (so the first 8 bytes were totally wrong), or maybe because you're trying to use zero_copy and haven't actually written those bytes yet (need to use #[account(zero)] before you've run .load_init())
It also can happen if you're trying to reference an account from a program that wasn't originally written in Anchor, and now you're rewriting it in Anchor. You might need to write some custom serialization logic for this.