It is a roundish object under the battery box

This vacuum line connects to something round under the battery box
1998 Dodge ram 1500 5.9 magnum, I marked these photos with red x's.
I need to know what this vacuum or emission line is called, and I need to know what it is connected to under the battery box.

 

It's hard to see from the pic, but it looks like the cruise control, if you have it. Just a guess!!

 

That is what it is. Thank you so much!

 

Vaccum lines simply suck pressurized engine air to use as a power source for something. Whether it’s emissions or fuel related, the vacuum system is an easy way to “borrow” air that’s being sucked in by the engine anyway. In the old days, some cars even used it to power door locks.