Yearly billing means you pay for 12 months of ProtoPie upfront and your plan is renewed on a yearly basis, unless you cancel it before the next billing date. Monthly billing means you pay for ProtoPie once a month and your plan is automatically renewed each month, unless you cancel it. With the yearly billing option, you can save a certain amount per year compared to the monthly billing option. For both the Individual and Team plan, you can switch from a monthly to a yearly billing option at any time in your account settings, under plan.