There are different Usages of the letter L.
1. the twelfth letter of the English alphabet
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
This letter denotes the next after K in a set of items, categories, sizes, etc. e.g. It also denotes the twelfth of twelve or more hypothetical people or things.
2. Roman Numeral
L = 50 in roman numerals.
L = Pounds a British Currency. L = Litre which is a metric unit of capacity, formerly defined as the volume of one kilogram of water under standard conditions, now equals to 1,000 cubic centimetres (about 1.75 pints). Besides, L letter of English Alphabet is used in Luxembourg as International Vehicle Registration. In some scientific notations especially stryctural chemistry L = laevorotatory as in L-tryptophan.
In Chemistry L = Avogadro's Constant and in Physics L = Inductance. In Biology, L = Linnaeus (as the source of names of animal and plant species). e.g. Swallowtail Butterfly papilio machaon (L., 1758) after the name of the scientist who led this naming system.
5. Universal Symbol of Left
L = Left where R = Right.
The most Common Noun which is used to learn this letter at the Nursery level is Lion; L for Lion.