A simple way to look at it is Titan are often associate with natural forces and phenomena, such as Eos, "Dawn".
The wiki for Eos may be confusing—there she is listed both as titan and god, but this is elucidating:
Titans are the order of god that is pre-Olympian specifically.
Helios, the sun, likewise, is one of the most famous titans. Tethys &...