Question for those who are familiar with AR-15's.

I just bought a lower receiver and need to buy some parts for it, but I don't know the parts names. If it helps, I'm buying a 6.5mm grendel barrel.<br> here's what I need to know if anyone can help. <br>1. If I start with only a lower receiver, I'd take it to a gun shop and they'd assemble the rest of it into a gun right? An AR-15 as it was originally designed by armalite?<br>2. A lower receiver is a gun in itsself, right? Am I correct in saying that the lower receiver is the firearm part, and everything else is a gun part? Like how a gun stock would not be a gun.<br>3. If I buy a lower receiver, I would still need to buy an upper receiver?<br>4. Rounds and cartridges are the same thing, right?<br>5. If I buy an upper receiver, that's what contains the barrel, right? Do the barrels come separate from the upper receiver, or is the barrel just part of the upper receiver?<br>6. The magwell is just the part that the magazine goes into, correct?<br>7. My dad always said with my 30-30, do not point the barrel at anything you don't intend to destroy. I suppose this applies to the upper receiver as well?<br><br>Thank you for your time, and I appreciate any help this may have been.