le, la and les are the french equivalents for the.
As French makes a distinction between "masculine and feminine objects", people use le for masculine things/persons and la for feminine things/persons.
However, in the plural, only les is used whatever the gender is.
- Le téléphone > les téléphones
- La télévision > les télévisions
When the following noun begins with a vowel, le or la becomes l'.
- L'ordinateur (m) the computer > les ordinateurs
- L'île (f) the island > les îles
NB: you may have noticed that making plural is easy: most of the time, it consists in adding an "s" to the noun.