For skateboards where the nose and tail are the same, you can skate either way. Mostly. However, if you skate with one end forward most of the time, then your bushings, trucks, and the deck itself will wear down in that direction. This is both good and bad - the deck wearing down and sinking into the way you skate means it will be more comfortable and intuitive. The skateboard becomes part of you even more. The drawback is that any bad habits you have will become harder to break, and skating a worn down skateboard has its own set of problems.
There is also the added weirdness that a lot of skaters like to apply their griptape so that there is an opening showing some of the board through right above the back trucks. This will make it harder to ride your board the other way, because you will likely want to put your foot in that exact spot, and there won't be any griptape there.
Some people like to make sure that they switch back and forth when skating, to make sure the skateboard wears evenly. Either way, it's always a good idea to try skating switch or fakie anyway. But the long and the short of it all is - it doesn't make a difference. But it does!