There are two types of wiring - coded version A or B. I haven't got a clue which they refer to but I have been using A for ages with no problems. Just be consistent and don't mix the two.
Either A-A or B-B can be used in a set up.
A cable with A at one end and B at the other is a crossover cable . You would use a crossover, for example, to connect two PCs directly.
Incidentally many routers these days will be happy to work with A-A, B-B and A-B but it is good practice to wire either A-A or B-B