What does it mean when the engine revs higher only when you turn the steering wheel?

the engine has to have a minimum rpm to continue running itself and all the other components of the car, when your idling it is close to that minimum. When your power steering is operating the engine is being robbed of some of its power, which causes it to increase its idle to compensate for the need of more power

Thank you Seth, however, it is not when the engine id idling, but rather while I'm driving, and perhaps "revving" is the wrong explanation for the noise it produces, it is more like a "whining", and only when I turn. Thanks.

you're getting low on power steering fluid

Yeah i imagine you are low on fluid... you may have a leak.

One thing i have learned about the 1MZ-FE (The V6 in your Camry) is that the power steering pump and boot are located directly under the rear cylinder bank head gaskets... so if your leaking oil theres a good change its damaging those components.