There are 3 main options for Photoshop now. Photoshop Elements is a basic version of Photoshop that is designed to be more user-friendly to a beginner but also offers far more limited functionality than the full "real" version of Photoshop.
Photoshop CS6 is the last version of Photoshop you can buy. It is a couple of years old now, but still pretty good unless you need the most recent version of Adobe Camera RAW (used for opening RAW files for the newest cameras) which is no longer available for it.
Photoshop CC is the current, and will be the ongoing current version of Photoshop. It is only offered as a subscription and costs $20 a month if you subscribe a year at a time or $30 a month if you get it month to month (may vary based on where in the world you live). If you have a very recent model camera and want to be able to open RAW files in Photoshop, this or possibly the latest version of Elements are your only options without having to go through some other tool first.
Note however that Photoshop is primarily targeted at advanced manipulation of images. Lightroom is the digital darkrooming package and is specifically designed for cataloging images and making bulk and rapid changes to RAW images. If you install Photoshop, it integrates with Lightroom and the recommended workflow is to catalog and do basic work in Lightroom and then when you need more advanced editing, you simply right click the image, choose to Edit in Photoshop and the image is sent from Lightroom to Photoshop automatically and when you save in Photoshop, the image is automatically stored in to your Lightroom catalog and associated with the source image.
Photoshop's Adobe Camera Raw doesn't offer any more options for RAW processing than Lightroom. They actually both use the same engine under the hood, so there isn't any advantage in moving to Photoshop unless the editing of the developed image is more complicated than LR can handle. Additionally, if you use the latest version of Lightroom as your darkrooming package, you don't need the latest version of Photoshop and have the option of using Photoshop CS6 even with newer cameras since Lightroom will take care of the RAW conversion for you.