The standard yoga mat is just 1/8 inch thick and can go up to 1/4 inch. Too thin and you can bang up your knee doing a crescent lunge, and too thick may cause you to fall over during say, tree pose. For travelers there are some that are 1/16 inch, making them easy to fold up and transport since they don’t weigh much.
Most are made of PVC, or vinyl. If you’re allergic to latex, avoid those made of natural rubber. For the standard option you might want to try the PVC since it’s the most common variety and also are the most forgiving with the most “give”, whereas jute and cotton have the least.
This can mean the difference between having traction and not.