Can someone tell me the difference between the "Auto" and "Manual" mode. I'm not sure what to set it at.

The manual mode means whatever is plugged into the timer has to be turned on or off manually (by you)
The auto mode means the device will turn on and off by itself according the times you have programmed into the timer.
It has the ability to hold 8 different programming times.
If you want it to come on and go off the same time everyday then you would only need to use one program.