Stitching "over 2" means stitching over 2 threads. It is how we usually stitch on linen and evenweave fabrics, as opposed to Aida fabrics. You can use either fabric with most projects, so if you prefer one over the other, substitute that fabric when the other is called for. A 14-ct aida is the same size as 28-ct linen, stitched over 2 threads (28 threads divided by 2 threads, since every stitch uses 2 threads, equals 14 stitches per inch).

Image 1

This is Aida cloth. Notice the squares formed by the warp and weft fibers. Cross stitches go corner-to-corner over the squares.

Image 2

This is a plainweave fabric: Annabelle by Zweigart®. Here is where we stitch over 2. The fiber comes up, then crosses over 2 threads horizontally, and 2 threads vertically before descending through the fabric. I find that once I get one stitch down, the others follow more easily.