Most textiles that are woven have a grain just like wood. They have a warp and a weft.
Bias- cutting along the diagonal of a fabric/textile
Inseam- measuring from the inside of your leg (by your crotch) to the floor. Depending on what you're making you want to check the length of the inseam with shoes on.
Bust-measuring around the body over the fullest part of the bust.
Natural Waist- measuring around the body where your belly button is
Hips- measuring around the fullest part of the butt/hips