From a tech-support point of view, SAP SUX!
SAP is a complete enterprise-management system that can handle purchasing, HR, inventory, sales, payroll -- you name it. SAP certification is among the most expensive in the business, running around $40k for complete cert. Don't get me wrong - being SAP certified is like sitting on a gold mine.
SAP is, from my experience, not very well written. It is a piece o' trash that (like Windows) everybody wants. That makes it popular. I don't understand it. SAP is hard to maintain, is extremely picky about what clients it runs on, and a SAP installation will increase your tech-support calls by about 25%.
If you're going into SAP support, you'll need to be certified. I don't think anyone will hire a SAP tech without certs. But, you may be able to come on as an apprentice and get the company to pay for your certification.
That's what I know about SAP. Oh - check out
http://www.sap.com