What does it mean when you have pain in the left side of your body?

It could be many things. Where it is located on your left side will make a difference too. High could be a lung problem, low could be colon or intestinal and in the middle a long list of possibilities including a strained muscle or gas. It most often takes more information than just the fact that it hurts to determine the cause. See a doc if it persists.

Definitely see a doctor if you're really concerned about it.

Your doctor's office or health insurance company may have a free nurse line that you can call to ask questions. Find out. You can also check with your local social services office for info if cost is a factor.

If you have a serious medical issue, it's better to consult with a doctor who can actually examine you.

The entire left side or a certain area? There are a lot of possible answers to that question. I would need more specifics in order to give you a solid theory. Of course in case your pain is serious, visiting an actual physician would be the best thing to do.