By strict definition, it means 'without knowledge', refering to deities. That is, an agnostic does not claim to have any definite knowledge of the existance of deities/a deity.
It is often said that agnosticism is a stepping stone to atheism. There is truth to this, as often the transition from theism to atheism is travelled through agnosticism. However, this is not the only form of agnosticism. Agnosticism can also develop as a rejection of both atheism and theism, for a number of reasons. All three discuss divinity in different ways, so it is foolish to say that agnosticism is simply a stepping stone to atheism, or undecided secularism.
He used to be Jewish, but after taking a philosophy course he became agnostic.
She calls herself an agnostic instead of atheist, because she finds them disagreeable.