SAP ABAP:
SAP is a full ERP systems' and business platform and then some. SAP is also the company who produces the business platform and associated modules (financials, general ledger, &c).
ABAP is the primary language in which most SAP software including customizations are written. It would do it injustice to think of it as COBOL and SQL on steroids, but that gives you an idea. ABAP runs within the SAP system.
SAP and ABAP abstract the DB and run atop various underlying DBMSs.
SAP produces lots of other things as well and even publicly says they dabble in Java and even produce a J2EE container, but tried-and-true SAP is ABAP through-and-through.
