Account activity is any credit or debit activity in a checking or savings account, or investments, withdrawals, dividends or fees in an investment account.
Account activity is the transactional history that will appear in ledger statements from a checking, savings, money market, investment, or other kind of financial account.
This usually refers to transactions that were originated by the account owner, such as buying and selling securities or withdrawing and depositing in bank accounts, but could also include activity such as dividends, interest, fees, and other sorts of automated activity generated by the custodial institution.
Accounts with no activity after a certain period of time are often charged an inactive account fee, sometimes also called a dormant account fee.