T-shirt vinyl is really fun and can be used for all kinds of projects, but the best one is of course making T-shirts. Using the T-shirt vinyl with your Cricut or Silhouette is very similar to using any vinyl. The exception is that you have to do everything backwards because you are actually cutting everything from the back rather than the front with regular vinyl. Check out the video below and it will make more sense.
T-shirt vinyl can be applied to just about any surface, as long as it can withstand the temperature of the iron. However it is best suited to be used on fabric. It is specifically designed for use on 100% cotton, 100% polyester, or 50/50 blends. So it doesn't really have to be used just on T-shirts it could be used on Polo shirts, hats, jeans, all kinds of clothing.
Part of the feature of working backwards with the vinyl is that the backing ends up acting as your transfer tape, so there are no extra items to purchase to be able to most successfully use it.
The transferring process with T-shirt vinyl is a heat transferring process. Sometimes this vinyl is called heat transfer or iron on vinyl. The vinyl itself has no adhesive that you can feel. When you remove it from the backing you can feel an adhesive that stays with the backing that is there just to keep the vinyl on the backing until the heat is applied.
To apply this vinyl you can go to all the expense of a heat press, but that is only realistic if you are in the production clothing making business. A basic everyday clothing iron will work just as well.