Lightroom and Photoshop are totally different apps, although there is some overlapping functionality.
Photoshop is the "industry standard" photo editor, and as such it's loaded with all sorts of tools and features, ranging from basic photo "tweaks" to sophisticated graphics tools, in fact, there is a whole lot of "stuff" that most "typical" photographers will have no need of.
However, if you really want "the best" in terms of photo editing capabilities, you can't argue against Photoshop.
But then some years ago two things of real interest to photographers developed:
First, digital photographers and digital image processors began accumulating increasingly large quantities of images and began wanting good organizational tools for their digital images, sparking a serious interest in "Digital Asset Management" (DAM). While there have always been "tools" for things like keywording and such, digital assets were an "open market" for a comprehensive "solution".
Second, as digital photography and technology advanced, the ability to capture and "develop" Raw files/data began getting a lot of interest. Adobe and some others put out dedicated software to process Raw files, including a special "plug-in" for Photoshop (Adobe Camera Raw), and people were finding that for much of their digital photo processing a good Raw processor could, in fact, handle much or even most of their digital photo work.
With those two things in mind, Adobe set out to develop a product that could meet the basic needs of digital photographers in an integrated and comprehensive way without adding to the "overhead" of the entire Photoshop "collection".
And so Lightroom came out, an app that included digital asset management built around the up-to-date Raw processor that is the "engine" of Adobe Camera Raw.
It should be added that Lightroom and Camera Raw were quickly modified to support the other common digital image types (tiff, psd and jpegs) and as a result, folks who weren't shooting Raws quickly came "on board" with a lot of enthusiasm since you could get good results with the processing tools, still without necessarily needing to resort to the Photoshop editor.
However, that doesn't mean that Lightroom is "right for everyone" -- some people get put off by the organizational features of Lightroom, for example. Some people prefer to stick with Photoshop and use Camera Raw for their basic/Raw processing. Other folks will use another Raw processor such as the Canon software Digital Photo Professional (DPP) and then will use an image editor such as Photoshop/Photoshop Elements or Paint Shop Pro or whatever.
My advice is to take your time, continue "reading up", and then realize that there are free trials for apps like Lightroom and Photoshop, so you don't have to just leap in!