As a statement it means "you have a computer"
As a question it means "Do you have a computer?"
¿Tiene usted un ordenador/una computadora? -formal ¿Tienes un ordenador/una computadora? -informal
"Una computadora" is one of the regional expressions for "computer". Others can be "un computador", or "un ordenador".
"A computer"
"You have a shirt."
Is there a computer in your class?
Tienes una hija = You have a daughter (Informal) ¿Tienes una hija? = Do you have a daughter? (Informal) If you wanted to say it formally, you would do: Usted tiene una hija = You have a daughter (Formal) ¿Usted tiene una hija? = Do you have a daughter? (Formal)
Do you have a social network or mail
Tienes (with an s) una nariz bolita = You have a pretty nose
"Tienes una novia" means "Do you have a girlfriend" in Spanish.
I think that you don't have a computer, lol. Take care, handsome.
You have a sweet look
It can mean "a" or "an", depending on context. It can also mean "one" describing a feminine noun. Example: Tengo una manzana. "I have an apple". Tú tienes una mesa. "You have a table". Yo tengo una. (referring to the table) "I have one".