What's the difference between monthly and annual plans

Wondering what's the difference between monthly and annual plans? 

• Monthly Billing Plans: renew every month and can be canceled anytime (for example, you can use it for only 1 month and then cancel). After canceling the renewal, you will not be charged again and can use any remaining requests until the end of your billing period.

• Yearly Billing Plans:  a single billing at the beginning of the plan for the next 12 months. It renews after the first 12 months. 

• Yearly Plans with monthly installments: (If applicable) a 12-month engagement with the ability to pay monthly. The annual amount will still be due.