We have central air and were standing next to the running air conditioner.

Katie:  What is that thing?

Me:  The air conditioner

Katie:  What does that do, condition the air?

Scot:  No Katie, that keeps the house cool.  Have you noticed that when it is hot outside, it is not hot in the house?

Katie:  The air must be piped in somehow then.

Scot and I (in unison):  Yes, through the vents.

Katie:  Oh, now I get it.  I only knew how window air conditioners worked.