1. Those that are rigorously proven through a number of means and hold true for all current known examples, but not proven as total fact due to the inability (at this time) to test all possible options. These are comprehensive in regards to what they relate to and are internally consistent and complete. Einstein's Theory of Relativity is one example.

2. Those that match empirical data and hold true for most known examples but are not comprehensive and do not fully explain what they're about. Darwin's Theory of Evolution is an example of this because it is not comprehensive in explaining all it relates to. His theory is seen as one of a number of mechanisms used in evolution, but is not the whole story. Also, there are cases that go contrary to what Darwin stated, thus it also fails to hold true for all known current examples. It's a good start, but not a complete answer.

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I gather from your statement's on belief you see shades of grey where I see black and white - to me something is or is not, it's proven fact or not proven fact, and a position taken on a basis without proven facts is a belief - regardless if it's for or against. Thus someone can believe something is so or they can believe it is not so, but it's still only what they believe.