Fusion as the name describes is the collective integration of best of breed softwares to simplify business needs. The revolutionary dream of Oracle claims to change the way we see business applications.
Some of the key technologies included are

UI Technology – ADF UI, ADF DI, ADF Mobile, DVT

Model Technology – Toplink, EJB

Backend Technology – Oracle Database, Essbase

Orchestration – Oracle BPEL Process Manager, SOA

Secuirty – Oracle Platform Secuirty Services,OPSS

Server – Oracle Weblogic Server

Customization – Oracle Metadata Services MDS

Aditional Technology – Oracle Enterprise Scheduler Services ESS, Oracle Business Rules OBR, Oracle Data Integrator ODI

and many more technologies from acquired products.