In QBO,what Is the Difference Between a Bill Form and an Expense

In QBO,what is the difference between a Bill form and an Expense form?

A) A Bill form records a services the company has received and has an obligation to pay the vendor later.An Expense form selects the bills a company wants to pay.
B) A Bill form records when the vendor gives the company a refund or reduction in its bill.An Expense tracks the products ordered from the vendor.
C) A Bill form records expenses paid for at the time the product or service is received via paying cash,check or credit card.An Expense form records services the company has received and has an obligation to pay the vendor later.
D) A Bill form records a service the company has received and has an obligation to pay the vendor later.An Expense form records expenses paid for at the time the product or service is received via paying cash,check or credit card.