Most of us are familiar with the French word(s) for the long before we ever start learning the language — or at least we have a vague idea that it involves an L.
There are actually four words for the. (All involve an L.)
Le goes in front of masculine nouns:
La goes in front of feminine nouns:
L' goes before a noun that starts with a vowel, regardless of its gender.
Les goes in front of plural nouns, regardless of their gender. (Note that the S is silent unless it's in front of a word that starts with a vowel.)