Below are the instances when we have to use "estar"

with talking about place and location
¿dónde está el cine?

where is the cinema?

estuve en la playa ayer I was at the beach yesterday.

with an adjective to express a temporary or unusual quality
Another way of saying this is: To express a quality or state seen by the speaker as subject to change or different from expected
la sopa está un poco fría

the soup is a bit cold

María está muy guapa hoy María is looking very pretty today
Hoy estoy de mal humor I am in a bad mood today

before past participles describing the result of an action
Note: the participle has to agree in gender and number with the noun.
el restaurante está abierto

The restaurant is open

la ventana está cerrada the window is closed

when asking someone how they are
¿cómo estás?

How are you?

estoy muy bien I am very well

with the present continuous
Carmen está bailando

Carmen is dancing

estábamos escuchando la radio we were listening to the radio