Calls possible on Ipod touch ?

I could not understand although i looked for it at apple site. the question is is it possible to make phone calls and recieve calls on i pod touch . There are some sites which tell how to modify it for this, but i want to know does it inherently have the feature. And then is there a SIM slot and what is face time. I could see in ad the faces and the camera but i couldnt figure it out.

Thanks