The Campus agreement with Microsoft covers a certain set of software on a campus-wide basis... software such as MS Office that is used by almost everyone on campus. The Campus agreement is an annual term 'site license' based on the number of faculty/staff/students covered. The Campus agreement requires renewal and payment annually to remain in effect.
The Select agreement with MS is basically a volume discount arrangement for software products not included in the Campus agreement. These products are not widely installed, but more limited to use in certain departments or on specific systems such as servers. UAB projects an annual purchase volume (by category, not by software title) and MS provides discounts based on that projection. Should UAB not meet the annual projections future pricing would be based on the actual level of purchases from the prior year.usually at a reduced level of discount. Most product purchased under the Select agreement is granted as a perpetual license with a single upfront payment. No annual renewal fee is required to continue to use the software, but maintenance/support is available as an option.
See the Microsoft Agreement link for more information on what is available under the Campus and Select agreements.