Final answer:
An ordinary annuity is received at the end of each period, while an annuity due is received at the beginning of each period.
Step-by-step explanation:
An ordinary annuity, also known as an annuity in arrears, involves receiving regular payments at the end of each period. For example, if someone receives a monthly pension check, it would be considered an ordinary annuity.
On the other hand, an annuity due, also known as an annuity in advance, involves receiving regular payments at the beginning of each period. This could be seen in situations like paying rent or leasing a car, where payments are made at the start of each month.