A bill or an invoice is a document created by the vendor asking the customer to pay.
Sometimes you are the vendor and raise an invoice asking the customer to pay. Other times you are the customer, and your vendors send you invoice asking YOU to pay.
It is generally accepted practice in accounting that all outgoing payments should have an invoice from a vendor. Also all incoming payments should have an invoice/receipt raised by you.
Whether something is an expense depends on what you are paying for. If the vendor's invoice is for goods that you are reselling, that is not an expense. That goes to inventory. Similarly when you pay an invoice from your heavy equipment supplier, that is not an expense, that goes to your equipment & machinery. However, when your vendor invoice is for something like janitorial service, utility bills, lawyer fees etc, these are classified as expenses and hence its 'expensed'.
It is generally accepted practice in accounting that all outgoing payments should have an invoice from a vendor. Also all incoming payments should have an invoice/receipt raised by you.
Whether something is an expense depends on what you are paying for. If the vendor's invoice is for goods that you are reselling, that is not an expense. That goes to inventory. Similarly when you pay an invoice from your heavy equipment supplier, that is not an expense, that goes to your equipment & machinery. However, when your vendor invoice is for something like janitorial service, utility bills, lawyer fees etc, these are classified as expenses and hence its 'expensed'.