Where can I read more about classifications?

Where can I read more about classifications? I don’t understand what each classification does.

  1. In ICOs, it’s common for one person to be the proxy wallet and send it to other people after they receive the token. How would I categorize these transactions?

  2. How would categorize an ICO transaction? would I mark the deposit to the contract? and if I swapped with Uniswap and their contract makes a deposit then how can I classify or associate that transaction to see the cost basis?

  3. How do I classify a transaction where I was paying someone back?

  4. How do I classify contract approval contracts or any contract interaction necessary to deduct the transaction fees?