This is a large application although there is a slimmer version, Photoshop Elements.
There is a saying, “if you don’t know Levels, you don’t know Photoshop!”
(Levels is an adjustment that allows one to alter brightness and contrast while it can also be used for colour correction particularly if one works in the individual channels)
I would like to add another saying, “If you don’t know Actions, you don’t need Photoshop!” since Elements will handle most controls other than automation.
Photoshop is about as important as the camera in professional photography these days.
It is a place where one can be truly creative not necessarily by creating clever montages and filter effects rather by allowing one to choose the exact colouration required.