Sph - Spherical Power of your correction. It means that the lens has equal power in all meridians, as if you literally chopped a slice off of a sphere
Cyl - Cylindrical Power of your correction. It means that the lens is shaped like a cylinder, so is flat along one axis, whilst perpendicular to this axis is idenctical to a Spherical Lens
Number - Cyl Axis, the axis that the cyl lens is being placed along (with the effective power in fact running perpendicular to this).
Astigmatism means that your cornea is more powerful in one direction than another. Hence the image will stretch in one direction or another, like looking at yourself in the hall of mirrors at a fun fair.
The cyl power is used to correct this stretching
