what is unlimited submission storage

Unlimited submission storage means that you can store unlimited form submissions for the forms in your account.

🔘 Submission Storage (total):  This is the total number of submissions you can store on your account itself, this is different from the first one which is a monthly limit. So for example, in "Free" plan, you are only allowed to have a total submission storage of 500. These 500 are the most recent submissions that you received. If you exceed your limit, the oldest submission data will be deleted, giving way for the new ones to be received.

Related Help Article: Understanding-Your-Account-Usage-and-Limits