"Over 2" means that you stitch over two squares of the fabric to make your X's. When you first begin to stitch"over one" on aida cloth you would first stitch from lower left corner of square to upper right corner, correct? By stitching "over 2" you would start from lower left corner of the square, skip the upper right corner hole but continue diagonally to the NEXT upper Right corner.

Hope this helps! :)

The term "over 2" usually refers to a design that will be stitched on a linen or linen-type of fabric. There are many different brands/colors/types of fabric that can be used for counted cross stitch. If you are a beginner, I would suggest that you purchase a simple kit that will include the fabric - and I would suggest aida 14 count. That refers to the type of fabric -- aida -- and the size of the stitches you will be taking -- 14 stitches per inch. Aida fabric has a very clearly defined structure to the fabric. The warp and weft (left/right direction and up/down direction) are very clear and the holes that you will use to create the actual stitches are very clear. With a linen fabric the warp/weft threads are much smaller and closer together and usually a much higher stitch count. For instance 28 or 32. Rather than stitching 28 or 32 very tiny stitches per inch, you stitch over two so you are only doing 14 or 16 stitches per inch. Once you've had some experience, you can stitch over 1. It's very time consuming but gives beautifully detailed results.

It's a little tricky to explain without having a picture in front of you. There are numerous tutorials available on how to cross-stitch. You might want to track one down and check it out. The term will be much clearer after that. Enjoy and good luck.