Over the span of 30 years, Photoshop has transcended it’s initial usage of being a “raster” or pixel based editor to having almost all the characteristics and basic tool set of all the other more specialized softwares in the Adobe collection.
It has the ability to deal with vectors, documents, animation, audio and even video; albeit it is not as sophisticated as the dedicated softwares which only deal with those particular types of files, it still provides a familiar environment through which users can get to know of the common tools that are shared by all the other softwares. So that the eventual transition from, say Photoshop to Illustrator or InDesign, feels smooth and effortless.
Being such a versatile software, the ways in which it can be used are also numerous. From basic editing, color-correcting, retouching, designing, compositing, animating and to basic video editing, the list goes on. So it is better to have a basic understanding of how everything works, and then later focusing on one or more particular aspects.
Once we are familiar with Photoshop, it can be used together with the other softwares too. As it belongs to a collection of applications, a Photoshop file, known as a PSD file can be edited or manipulated in other creative applications which deals with another part of the whole project.
Furthermore, it can be used for basic everyday usages ranging from cropping and changing the background of a photo for ID tags to making presentations of PDFs. There may be applications that can automatically do these tasks for you, but it is essential to have the knowledge of how it happens, so that if something doesn’t look the way it should, you can always rely on your knowledge rather than some applications’ code.