Conversation so far:
what is the delta ii technology used for
The Delta II is used to launch small to medium payloads to geostationary orbit.
has the Delta II launched anything famous
The Delta II has launched such spacecraft as Near Earth Asteroid Rendezvous and the Mars Exploration Rovers.
is there a third version of the Delta II
The Delta III, an 8000-series rocket, was designed in the late 1990s.
is there a fourth version of the Delta II
The Delta IV, which entered service in 2002, has little in common with its predecessors.

Question: what made it different
Self-contained rewrite: what made the Delta IV different from its predecessors