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Deposit: A transfer from a private/individual account to official exchange account*

Withdraw: A transfer from an official exchange account* to a private/individual account.

* ie. an account on a list of known exchange accounts

these are just transfers from hive to the exchange and back I presume?

They are transactions of type "transfer" recorded on the Hive blockchain between Hive accounts. Exchanges need to have a Hive account (eg. @deepcrypto8, @bittrex, @upbitsteem) to receive Hive deposits and to facilitate withdrawals.

Thanks, that clears it up for me. I thought so, but wasn't sure! :)

Yes it is transfers to exchanges hive wallets and back

Thanks! Makes sense now.
Great work, very useful :)