Recording Acoustic Guitars (noob content inside)

[DanLights]

I logged in to post a thread about acoustic/electro-acoustic guitar recording and found this one, nice! Great info here

Also, make sure that the player is not muting the top of the acoustic with his palm or forearm. This will destroy the low end. try it you'll be surprised.

i always run a small diaphragm condenser on the 12th and a large on the body behind the bridge.

Could you please explain this? I don't understand, how do you mute the "top" of the acoustic? in other words, what is the "top"? (I do know the meaning of the word, I mean what are you talking about when you say the top of the guitar)