Warp & Weft
How your patterns are laid out on your fabric for cutting makes a very big difference in how the garments will wear and drape.
The background of the image above is a real piece of fabric that has distinct threads. Most patterns are laid out like the image. The grainline on the pattern is lined up with the warp threads. This is referred to as laying the pattern "straight-of-grain" and it gives a garment structure. It will hold its shape because it is square to the threads. You can also line the pattern up on the weft threads, if you want.
There is another direction to fabric called the Bias. If you lay out your pattern on the bias, it will lose its structure. The warp and weft are 45° out of square and the garment will buckle more easily.