iPhone 4s doesn't turn on
First timer here, and I have an iphone 4s that doesn't turn on. I don't know what happened, it didn't fall or anything it just stopped working. It doesn't turn on and gives no indication that is charging. I googled to try to solve this and I tried home+power trick but it didn't' work. I tried plugging it to the wall and do the home+power and it didn't work either. Now, I don't know if it's the battery that's dead (I would assume that it would still light up the screen when I plug it to the wall) or if it's just a disconnected screen or what is it.
I would really appreciate any help.