My son is 3 yrs old and in 5 months he will be 4 but he is still not talking well.I have heard other kids his age or younger talk and they talk a lot more then him and a lot more clear then him. I am worried I don't know if this is OK or normal but he doent understand a lot of things to, he only understands simple things like "throw this in the trash" or "lets go to grandmas" and he tries explaining things to me but we just don't understand him .what can I do?

What does your family doctor say? Have you had his hearing checked? I suggest checking out with the doctor to see if there is a medical reason and then you can go from there.

I agree here. I would also add don't panic, every child does not develop the same. In addition if you currently speak to him in baby language STOP and start talking to him as you would any other adult. Enunciate all your words with him with emphasis. This will help the young lad out. Keep your head up and don't get discouraged.