I will explain with examples in these 2 sentences. 1)The children remained silent when they saw the principal walk through the corridors. 2) Paintings made by children were put up all along the corridor walls of the school.

The difference is that you would commonly say 'along the corridor' but it is difficult to imagine a situation where you would say 'through the corridor'. I could perhaps imagine saying something like: 'there were posters pinned on the wall 'throughout' the corridor.'