Annual: Prepay for the year and get two months free. You also get access to the entire annual quota at once with no monthly limits. Quota refreshes annually upon renewal.
Monthly: Month-to-month billing with no commitments. Quota refreshes monthly upon renewal and is 1/12 the annual quota.
Annual-Paid-Monthly: Just like the annual billing, this option provides access to the entire annual quota at once with an annual commitment. There are no monthly upload limits. Account is billed monthly at the same price as the monthly billing. Cancellation fees are only applied if usage is over the monthly average. For example, if you used 50% of your quota in 6 months, there would be no cancellation fee. However, if you used 50% in just 2 months, you would be charged for an additional 4 months.