[Plutoburn]

Is it just someone who is a stand out in the division or someone who has a decent chance of dethroning the champ?

There are times when a fighter fits both criteria, but there are also times when someone who is a stand out in the division, but has very little chance of beating the champ, ie) Karo vs Hughes, Buentello vs AA

Aurilo is a really bad match up for Gomi, but he is not exactly a stand out in the division, though he won a shocking victory over Gomi, that doesn't mean he would dominate the rest of the division.

Someone who is fighting for the title is a challenger, does contender automatically equal challenger?

[Frank Le Animal]

Sometimes