Basic rundown (albeit lengthy) of Intuos products, sorted by tier based on basic needs and cost (note that this is just me listing stuff off the top of my head, I'd suggest going to the official Wacom website for more accurate info):
Intuos Pen/Pen and Touch/Manga: Basic drawing tablet that costs around $100 + tax. This is the line that replaced the Bamboo line, ex. the Capture modeles. Doesn't come with express keys. The bare basics, but still gets the job done (I used a Capture for years, loved it <3) Definitely what you should be getting if you're still new to tablets and just draw as a hobby or for studies.
Intuos Pro's: One step up from the Pen/Pen & Touch/Manga; costs around $300-$400 (if I recall correctly), has customizable express keys and more pressure sensitivity detection for the pens. I found that the express keys were sort of pointless though, seeing as how it's a desk based tablet and one hand would be using the pen, with the other on the keyboard for shortcuts ... but that's just me. I find the express keys far more beneficial for something like the Companion 2 when your hands are ALWAYS holding the tablet, with the buttons on the left side (or right if you're left handed). Still, great tablet, especially if you're looking to kind of up your game. If you have the money to throw around and want a more advanced tool, this is where you want to go. Get a medium size; large sizes are pointless for desk tablets, as it's just unnecessary space (especially because the tablets configure to your monitor screen anyway).
Cintiq's: Digital display tablets. These are much heavier duty drawing tablets that are typically used by those who either a.) have tons of money to throw around, or more commonly, b.) do a lot of industry work and basically make their living off their work and need a more professional tool with a more powerful kick. They fall into a few more categories, mainly the following:
Cintiq HD's (ex. 22HD, 26HD) are high-definition monitors you plug into your working computer and use as a monitor to draw on. Come with express keys and a higher level of pressure sensitivity detection. Good for those who work professionally in an office, either at home or in an industry profession. These cost well into the $1000's, depending on the model. Very sturdy so long as you take care of them, and seeing as how they're built to have a pen pressed to the screen 24/7, they're good at taking a lengthy drawing beating.
Cintiq Companions, high-definition computer-based drawing tools where, instead of plugging in a digital display tablet to work on into your main computer, the Companion is the computer, and you draw directly onto it. Available in two formats - PC based, pre-installed with a copy of Windows, and Android-based, so it works more like an app-based tablet. Price ranges, starting at about $1600, depending on the model (with different capabilities for different programs; some are built for casual use and sketching, some are built for 2D animation, others are built for more heavy duty 3D and modelling work). The Companion 2/256 GB is the model I use :> It's the most "well-rounded" in the sense that it can run everything you need, from animating to modelling to video gaming, unless you really need to render farm, in which case, you'd need to go for something higher that can handle the strain of doing so. These computers are, of course, more meant for artists that are on the go and travel a lot, or just prefer having a portable system vs. a home-based platform. If you can't see yourself using a portable drawing device that's a bit on the smaller size compared to the HD models mentioned above, then look into the HD models for larger space and more comfortable desk use; if you have the budget, of course.
Of course, all of that is, as I said, listed off the top of my head. There are a ton of different models and makes of tablets, so there's always a tablet out there for someone that fits their workflow and needs.
Source: I have used all of the base tablet lines - the original Capture line (my first tablet <3), the Intuos starting line (more or less test drove that one), the Intuos Pro line (we got Intuos Pro 4's as work gifts when we started our college year), and am now currently using the Cintiq Companion 2 (after saving up arduously for months and using a good chunk of my student loans as well to purchase it lol).
IMPORTANT NOTE: The touch feature? Totally pointless unless you're using a Cintiq Companion, and even then, it's STILL always a pain in the ass that I keep turned off nearly 100% of the time lol Tablets with express keys make it easy to alternate between having it off and on, but seeing as how the Pen & Touch in the starting line doesn't have express keys, I would HIGHLY RECOMMEND NOT GETTING THE PEN & TOUCH and just get the Pen/Manga tablet if that's the line you're interested in! The touch function is just very unnecessary; most of your mouse work can be done with your tablet pen or a mouse, both of which are far less annoying and far more accurate than using your finger (especially when you're trying to draw ... it's such a pain to have the tablet try and read your arm while you're just trying to sketch :IIII )
also another important thing i should mention
The biggest perk to digital display tablets are their convenience. That being said, your art will not magically improve if you shell out thousands for a Cintiq product. Whether it's the convenience of being able to work directly on a screen or have your tablet with you wherever you go (in the Companion's case), it's still all just for the sake of convenience. Desk tablets are no different, they're just built for different methods. They will still get the job done. So don't feel like you're amateur or anything for using an Intuos Manga or a lower-end tablet; whatever gets the job done should be considered a good tool on your end. Just don't feel like the more expensive tools are the ones that are going to skyrocket you and your artwork into success, because, well, that's how the companies sucker you out of your money lol Many of my best works have been done with desk tablets, and I still use them from time to time. Your art shouldn't be affected either way, so get the tablet that works for your workflow, your budget, and your preferences