It is the feminine plural form of "todo," which means "all" or "everything."
Here are some examples:
* Todas las mujeres: All the women
* Todas las casas: All the houses
* Todas las frutas: All the fruits
* Todas las noches: Every night
* Todas las veces: Every time
It's important to remember that "todas" is used when referring to multiple feminine nouns.
For example, if you are talking about all the cars, you would say "todos los coches" (masculine plural), not "todas los coches".