Photoshop is a software tool for editing pixel based images. It can use vectors and some 3D information bit it is primarily aimed at manipulating 2D raster images.
Photoshop uses layers that stack on top of each other. Different adjustments can be made to each layer to then combine to form a unique images. Layers on top override layers on the bottom. Masks can be used to have adjustments only affect part of a layer. Layer blending modes can affect the way layers stacked on top of each other. Affect the layers below them.
So much I spent sand filters can be made into smart filters that are non-destructive, meaning that they can continue to be edited without losing any image quality. You can’t go back.
Pixels vs Vectors
Pixels are resolution dependent while vectors have infinite “resolution” since the visual output is derived from mathematical equations.