A single hole plate is just that, a small circular hole just a bit bigger than the needle to go thru. The other plate is a zig zag plate where the opening is oblong to allow the needle to go down in various places as it makes the zig zag (or decorative) stitch. With the larger hole plate, your fabric can actually be forced into the hole, people say that it's 'eating' the fabric. This may jam your sewing. The single hole provides more support for the fabric giving you a better stitch quality. If your machine only does straight stitches, you probably have a single hole plate. One caution. If you do change to a single hole, put a sticky note or other identifier on your machine so you don't change to a non-straight stitch. Best case, the needle will break or bend, worst case, you will throw your machine out of time requiring an expensive repair. You would have to contact your manufacturer to see if a single hole plate is available.