100 payments per month, what does that mean?

what does that mean?  We are a 501c3 org and would love to use your capability to collect membership and other fundraisering information. Not sure what level to subscribe 

How many payments are you expecting to receive per month? If you are expecting to receive more than 100, you should upgrade to Gold plan, which allows unlimited payments, because if you reach the allowed monthly payments limit, you won't be able to receive more, until the counter resets on the first day of the following month.