Both Presale Access and Discount Codes have two distribution styles - either Multi Use Codes or a Single Use Code.
A One Time Use Code can only be used once by one customer, and then it will not work again.
A Multi-Use Code can be used multiple times by any number of customers.
For example, sometimes a site may offer a code like "SUMMER" that anyone can use. This would be like a Multi-Use Code.
Sometimes, you'll get an email from the site with a personal code like XY4F5RT3 that is only for you. This would be a One Time Use Code.