Sph means sphere and determines the spherical power of the lens. If the value is negative it means that you are myopic or "short-sighted", if the value is positive you are hyperopic or "long sighted".
BC means base curve and determines the radical curvature of the back surface of the lens.
Dia means diameter and tells us how far it is straight across the lens from edge to edge.
If the lens corrects astigmatism besides myopia or hyperopia there are additional markings on the box.
Cyl means cylinder. This number tells us how big astigmatism the lens corrects.
Axis determines in which direction the astigmatism lays.