The online activity page contains all transactions initiated via online banking including single transactions, recurring transfers and mobile deposits, but does not include transactions made via other means, such as ATM or debit/credit card transactions. This page also shows the status of each online banking transaction as it moves from a drafted status to approved, then processed as well as authorized or cancelled.
In contrast, the account history page is a record of processed and cleared transactions against your account from all sources, not just online banking. Additionally, account history does not include transactions that have been drafted/approved/cancelled via online banking, but only those that have already cleared or will clear your account the next processing day.