A.)  Primarily, the auditors want you to be able to prove that valid licenses for each specific product are present and that the number of licenses you are contracted to possess matches or exceeds the number of copyrighted products you have loaded on your systems. Second, and every bit as important as the first, they will closely examine your receipts & proofs of purchase, certificates (stamps or proofs) of authenticity to determine if the products you have purchased are legal and not counterfeit. (There is MUCH more to audit documentation, but this description will at least get you started.)

Do you want to know more? 

Here is a very valuable resource for you: Take a look at the Table of Contents (TOC) of my book: Modern Pirates. This is the only book where you can gain a complete vendor-neutral overview of the software auditing industry.  In Pirates, I discuss the audit process, the identities of a majority of audit enforcement groups as well as their tactics and the processes you can use to stonewall the audit.  At the very least, through the simple information you'll find in Pirates, you'll be able to drastically cut the financial impact of the audit.