Practically, in actual Greek myth, there are few differences between them. The line between Titan and God can get a little fuzzy. More specifically, the word "God" could probably used to describe both, but I'm sure you mean the Titans and the Olympians.
It comes down to this. The Titans were the children of Ouranos/Uranus (however you want to spell it), who was the personification of/God of the Sky, and Gaia, the personification of/Goddess of the Earth (this gets a little weird when you find out the Gaia was also the mother of Ouranos). So, they have a group of children, the Titans, and they're beautiful and strong and awesome and everybody loves them. Then, Ouranos and Gaia have more children, the Cyclopes (immortal, one eyed-giants), and they're big and strong but kind of ugly, and Ouranos wasn't happy about that. Then, they had a third set of children, the Hecatonchires (fifty headed, hundred handed giants), and they're the strongest of all, but ugly as sin. Ouranos stuffs all of the ugly children back into the Earth Mother's womb because he can't stand the sight of them, so Gaia asks Cronus to overthrow his father and release his brothers and sisters.
There is a big war and the Titans win! YAY! Ouranos either gets cut up to pieces or just gets castrated (which apparently falls into the ocean, and from the blood and semen that mixed with the ocean water comes Aphrodite, goddess of love... so yeah... that makes sense...). Cronus becomes King and... doesn't release his brothers because apparently he takes after his dad and can't stand ugly people either.
Zeus (son of Cronus and King of the Olympians) later released the Cyclopes and Hecatonchires in his own war to overthrow his father. Good move, as the Cyclopes (those who were sons of Uranus and Gaia, anyway) and the Hecatonchires were all stronger than the Titans and Olympians, anyway.
So we've got the Titans. They are all of the children of Gaia and Uranus who weren't one-eyed or fifty headed and hundred handed... also all of their own (the first generation Titans') children, EXCEPT the Olympians, the children of Cronus and his sister Rhea. This is an important distinction, as all of the children of the other Titans are still considered Titans. Many of their grand children are considered Titans as well, but at that point that just start to call them Gods, because most of the important Titans lost the war against the Olympians and were put into the prison of the Underworld, Tartarus. Those who weren't had sided with the Olympians, so I suppose they decided to stop calling themselves by that name so as to distance themselves with the previous regime.
In short, the Titans are the children and grandchildren of Gaia and Uranus, excluding the children of Cronus and Rhea (who were the King and Queen of the Titans), who called themselves the Olympians.
As to their abilities and status... I can only say that they're probably approximately all as strong and weak in relation to each other as family members within a mortal family are. The warrior deities and ruler deities are usually the strongest, the goddesses are usually weaker. The Titans were the former ruling regime, and the Olympians overthrew them, and now they're in prison for all eternity. As such, I don't imagine the Titan's status is consdidered very high.