Types 

Stretchy Wraps -a long piece of fabric usually but not always one size fits all. Mostly used for newborns and front carries as back carries in stretchy wraps a not recommended. 

Common brands include Moby, Sleepy Wrap, Hot Mama,  and my personal Favorite Wrapsody-Gypsymama Bali Baby Stretch

Woven Wraps- Machine or hand woven fabric that usually has only a slighty diagonal stretch. Standard sizes include but are not limited to( 2.7m , 3.2m, 4.2m , 4.6m, and 5.2m )            

Depending on your particular carrying needs you can find a wrap that is thin and grippy ( which is great for rucksacks and rebozo carries) or a nice thick and cushy long wrap ( great for beginners)  So the brand you buy for one use might not be good for the other.

These wraps can be fairly expensive but you only need one good wrap to do a variety of carries.

I suggest a 4.6m for most women if you are a little fluffy or preggo you can go up a size 5.2m to do most carries. I love long wraps so if I can find a wrap manufacturer that runs long or sizes them to 4.7-4.9m I grab it up.

Common Brands include- Hoppediz (what I tend to use the most) , Storchenwiege, Didymos, NatiBaby, Wrapsody- Bali baby Breeze, Ellaroo, and many more