Training pants aren't a necessity. Some parents continue using diapers until their chid has mastered using the toilet. I have personally always used cloth training pants because it gave my child a sense of being a big kid. There are multiple styles to choose from. So where do you start?
If you're just starting out you might want to try a waterproof option with side snaps. Why? It's easier to remove a poopy accident if you can just open the sides instead of pulling pant down. If your toddler feels the rise snap type resembles a diaper; choose a pair that has a smooth front without the snaps. We have a side snapping toddler diaper that has suede cloth lining and inserts. Your child will not feel the wetness as much due to the lining so this is a good option if you're just starting or want something you can use during naps. I also have flannel lined side snap training pants with a pocket and a sewn in soaker. These will feel wet to the touch.
Waterproof pull on pants are a good option for those who are a little further on in the toilet learning process. They'll tend to contain accidents a little better than plain cloth style. The cloth training pants with bamboo terry lining as well as the pants that have the wide sewn in soaker will contain one urine accident and for many tikes; their outer pants will not get wet. These will not work for multiple urine accidents. They will have to be changed after one pee.