This tool allows you to forego your computer mouse for a stylus (penlike tool below). Some artists will use the stylus & pad to draw or paint images right into the computer and for such an approach the Wacom is invaluable. I, however, do all of my initial artwork outside of the computer, so the Wacom's obvious benefit of more authentic art isn't my main reason for affection here. In fact, it is really my right hand that's in love with the Wacom. Intense work on the computer with a mouse can make your hand cramp & throb after endless hours of clicking & dragging & clicking & dragging. Working with a stylus is just a lot more comfortable. A lot more!
And there are some pretty cool secondary features too. The graphics tablet is pressure sensitive. So, if you have an art program that's compatible with this feature, you'll find that with some paint brush tools a stylus will create a varied stroke in response to the pressure you apply. This is the case with Painter, Illustrator, etc. No settings to change. A normal computer mouse will just produce an even line.
The buttons in the corners can be programmed to do whatever functions you regularly use. And the longer rectangle (see top photo) allows you to zoom or scroll if you stroke your finger across it. I have my buttons disabled as I'm all about key commands. But I still think they're cool.
So that's the Wacom. I have one huge tablet, as wide as my keyboard, and a smaller one to take with my laptop. As I said before, I couldn't do without it, so I had to have a second one for travel.