Hot aka shortcut keys are combinations of keys you
can hit to preform actions more quickly than selecting the option from the menu
with your mouse. These are only ones I have memorized and use frequently to make
my photoshop opertation much more efficient.
Ctrl + C - copy selected area.
Ctrl Shift + C - copy all layers of the selected area.
Ctrl + V - paste whatever you copied.
Ctrl + X - cut selected area.
Del - clear the selected area.
Ctrl + Alt + Z - go a step back.
Ctrl + Shit + Z - go a step forward.
Ctrl + N - new project.
Ctrl + O - open file.
Ctrl + S - save.
Ctrl + Shift + S - save as.
Ctrl + Shift + Alt + S - save for web.
Ctrl + P - print.
Ctrl + E - merge selected layer down.
Ctrl + Shift+ E - merge selected layer down.
Ctrl + + - zoom in.
Ctrl + - - zoom out.
Ctrl + A - select all.
Ctrl + D - deselect.
Ctrl + I - invert selection.
Ctrl + Shift + U - grayscale/desaturate selected layer
If you find this information inaccurate or have questions
post in the forums