Sewing patterns will commonly refer to fabrics as having either 1 way, 2 way or 4 way stretch. Some companies will have a different method but here at Super Cheap Fabrics, here is how we classify a 1, 2 or 4 way stretch.
The first thing to note is that all fabrics will have stretch along the bias or diagonal of the fabric, no matter the type.
This will have stretch along either the vertical or horizontal part of the fabric.
This will have stretch along both the vertical and horizontal part of the fabric.
This is the same as a 2 Way, but it just makes reference to the inherit stretch along the bias/diagonal part of the fabric which is part of all fabrics!
So, in conclusion - we refer to fabrics as having 1 or 2 way stretch. If your pattern says 4 way stretch, you need to look for a 2 way fabric.
Here's a little video by Zerrin further explaining this and showing some examples: https://www.youtube.com/watch?v=L4h49RC9oEU&t=36s