SAP BW (business warehouse) now remains history since SAP change the name into SAP BI (BI stands for Business Intelligence) in new versioning of 7.00 or 700 under Netweaver 7.0 (also called as Netweaver 2004s / NW 04s) engine. Currently there is SR2 (service release 2) for the engine version and seems there would be SR3 or SR4 before going to NW8.0 / NW9.0 or ECC7/ECC8. There are a lot of upgrade activity projects from previous BW release such as from BW 3.1 or 3.5 to the latest version of BI.
NW 7.0 is also used for ERP (enterprise resources planning) ECC6 (also known as mySAP ERP 2005). The difference is business content and configuration added / installed into the engine in the form of business Add-ons (basis people known this through transaction code SAINT for its installation). In ECC there are business modules like FICO / finance - controlling , MM / material management, SD / sales and distribution, etc while not available in BI.
BI also needs additional engine component such as AS Java, BI Portal, etc for standard scenario, while ECC doesn't need it. Under BI, we can also install additional scenario such as SEM (strategic enterprise management) and its sub module such as SEM-BCS (SEM business consolidation) or IP (integrated planning).