Accuquilt is the manufacturer of the GO! and Studio fabric cutters. This type uses a die which consists of a sharpened steel blade embedded in a wood or plastic base. The blade is bent to cut the shape of the piece. Each die is a 'one trick pony' it will cut only shape(s) it's made for. The die, fabric and a cutting mat are sandwiched and inserted in the machine where pressure is applied to force the fabric into the blades. The dies can be pricey, so this type of cutter is good for shapes that you are going to cut lots of: squares, triangles, apple cores etc. They can cut multiple layers of fabric in a single pass, making quick work. They do make shapes that you can use for applique (flowers etc.) but unless you are planning to do a lot with that shape it may not be cost effective. Other manufacturers besides Accuquilt make these too. An example is the Sizzix BigShot. The dies vary in size and thickness, so you need to check that the die you purchase will fit your cutter.
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The other class of cutters are computerized. The Cameo (Silhouette is the manufacturer), ScanNCut (manufactured by Brother) and Cricut (manufactured by Cricut!) are some examples. There are others. Basically the unit cuts a shape that is supplied by a computer file. They only cut one layer of fabric at a time, so are great for appliques that will be used for only one project. It certainly is possible to cut an entire pieced quilt, but it takes a bit of time and dedication. The machines vary in the files that it will accept. Some will only cut shapes from a cartridge provided by the manufacturer, some will also scan an image and cut it and some have a program that runs on your PC that will let you draw what you want, then cut it. Almost all will let you enlarge or shrink the shape and place it exactly where you want on the fabric. They are very flexible, but are better suited for smaller quantities of cuts.
I have the big Accucut studio cutter and don't think I could quilt without it! I don't find any more waste than when using a rotary cutter. It all comes with practice and a little forethought.