Canon EOS Rebel XTi Instruction Manual page 51

Advanced Shooting
Techniques
In the Basic Zone modes, most functions are set
automatically and cannot be changed to prevent spoiled
shots. In the <
P
> (Program AE) mode, you can set
various functions and be more creative.
In the
<P>
(Program AE) mode, the camera sets the
shutter speed and aperture automatically to obtain the
standard exposure.
. l ffI>
The difference between the Basic Zone modes and
<
P
>
is
explained on page 158.
*
<P>
stands for Program.
* AE stands for Auto Exposure.