intake manafold questions

On the back of the intake manafold there is a small box type thing dose anyone no what this is called? part of it is about the size of a "D" battery and it mounts right on to the manafold, it has a tube for air or sumthing that goes in to it and a wire plug in for it.
Also does anyone know how i can be positive that i have the right electrical wire pluged in to the back of it because i found another identical wire that fits in to that slot.

Can you give a little more detail....did you unplug something by mistake? Were you swapping out a part? etc.