It translates to "they have" or "they own".
Here are some examples:
* Ellos tienen un perro. (They have a dog.)
* Las chicas tienen muchas amigas. (The girls have many friends.)
* Los estudiantes tienen que estudiar para el examen. (The students have to study for the exam.)
It's important to note that "tienen" is often used in different contexts and can have other meanings depending on the sentence. For example, it can also mean "they are" when referring to a state of being.