OD is short for the Latin term oculus dexter which means right eye.
OS is an abbreviation of the Latin oculus sinister which means left eye. You'll often see this terms on eyeglass prescriptions.
Sphere:The sphere (SPH) on our prescription indicates the lens power you ne. to see clearly. A minus (-) symbol next to this number means you're earsighted, and a plus (4-) symbol means the prescription is meant to correct farsightedness.
Cylinder:The cylinder (CYL) number indicates the lens power needed to correct astigmatism. If this column is blank, it means you don't have an astigmatism.
Axis: An axis number will also be included if you have an astigmatism. This number shows the angle of the lens that shouldn't feature a cylinder power to correct your astigmatism.