Sergeant is a rank used in most militaries, police forces, and other uniformed organizations around the world. The word comes from the Latin serviens, "one who serves", through the French term Sergent.
A Lance-Sergeant (LSgt) was originally a Corporal doing the work of a Sergeant. The job is now used mostly in the Guards, where it is given to all Corporals. A Lance-Sergeant in the Guards and Honourable Artillery Company wears three chevrons, and is considered senior or higher up to "normal" Corporals. For most purposes, he still remains a Corporal rather than an acting Sergeant (e.g., he will typically command a section). In the Household Cavalry, the same rank is Lance-Corporal of Horse.