Contact Lens Terminology
Power on your contact lens prescription is a number, (dioptres), that starts with a + or - sign. For example, +3.50, -2.75 etc. This is to correct either your short-sightedness if it is a (-) sign or long-sightedness if it is a (+) sign.
Base Curve, (BC) is a measure of the curvature of the contact lens. This makes the lens fit correctly on your cornea.
Diameter (DIA) is a measure of the size of the lens. Sometimes, a lens is manufactured in only one base curve or diameter. Your optician may then have omitted this value on your contact lens prescription since it makes no difference anyway.
Cylinder (Cyl) is the strength of your astigmatism. If you have a number for cylinder on your prescription you should look at Toric Contact Lenses.
Axis Is the direction of your astigmatism. 90 and 180 are the most common.
Add is the correction needed for bifocal / multifocal / progressive contact lenses. This number refers to the reading strength of the lens.
Colour is the colour of the contact lens and is only needed if you are buying coloured contact lenses. The colour does not affect your prescription in any way.