Flydreamer,
V1 is the take-off decision speed. It is the minimum speed from which it is possible to complete a safe take-off in the event of a single engine failure. It is also the maximum speed at which sufficient field length remains available to bring the aircraft safely to a halt if the take-off is aborted. If the pilot has not already started to abort the take-off when the aircraft reaches V1 he/she must continue the take-off.
VR is the rotation speed. It is the speed at which the pilot must pull back on the control column to bring the nose of the aircraft up into the take-off attitude. The term "initiate rotation" means starting this nose-up manoeuvre.
VLOF is the lift-off speed. It is slightly higher than VR and is the speed at which the aircraft first becomes airborne.
V2 is the take-off safety speed. It is the minimum speed that must be achieved by the time the aircraft reaches screen height following a single engine failure detected at V1. If none of the engines have failed the aircraft must reach a slightly higher speed of V3 by screen height.
The term "screen height" refers to an imaginary screen of a specified height at the end of the take-off distance. The height of this imaginary screen will be either 50 ft for small aircraft or 35 ft for larger aircraft and multi-engine jets.
Please do not hesitate to ask more questions if feel the need. Those members who do not wish to read them can simply scroll down.