One of the first "technical" terms I learned when I started sewing was "selvage". Selvage is the woven edge of fabric.
When you buy a length of fabric, the sales person will measure out the length you want along the selvage, and then will cut it from the bolt by cutting crosswise from one side to the other - cutting from selvage to selvage.
If we buy 2 yards of 44" inch-wide yellow fabric, we'd have a piece that would look roughly like this:
When working with simple quilt designs, such as my recent "Summer Breeze" quilt (below) I check for the crosswise/lengthwise grain when I lay the blocks out.
Then I stitch the squares together, joining lengthwise edges to lengthwise edges. After that, when I join the columns together, I am sewing down on the crosswise (more stretchy) grain, and it's easy to get the corners lined up without pinning (I just stretch one side or the other to get the corners perfectly aligned).
Once I became aware of the weft/warp stretch, my quilting life certainly became easier!
Writing this post was especially fun. As a self-taught seamstress/quilter, I knew what I wanted to share with you, but didn't know the technical terms (other than "selvage"). I did a little research on Google to get the terms weft, warp, crosswise grain and lengthwise grain. I'm not sure well I'll remember those new terms, but I sure don't forget the concept.