Is expense account a debit or credit account?

Expense account is a debit account.

So for example the expense is rent paid, so every year the rent expense increases and we record it in the debit side of the rent payable account and to complete the double entry, credit the same amount to the profit and loss account.

Follow this basic rule to know which side your looking for: DAXP (debit side items), LICS (credit side items)

D: drawings A:assets X:expenses P:purchases, L:liabilities I:income C:capital S:sales.

So DAXP items increase in the debit side while LICS items increase in the credit side.