Both verbs ser and estar translate to essentially the same verb in English: to be. There are two easy acronyms that you can use to remember when to use each one.
Descriptions – El libro es interesante. The book is interesting.
Ooccupations – Ella es doctora. She is a doctor.
Characteristics – Yo soy alto e inteligente.I am tall and intelligent.
Time – Son las dos y media. It is two thirty.
Origin – Nosotros somes de Colombia. We are from Colombia.
Relationships – Ella es mi hermana. She is my sister.
*If you remember one thing about ser, remember that it is used mostly for characteristics and to define the qualities of something.
Position – Ella está a mi lado. She is at my side.
Location – La casa está en la esquina.The house is on the corner.
Action – Yo estoy hablando. I am speaking.
Condition – Estamos enfermos.We are sick.
Emotion – Ellos están felices. They are happy.
*If you remember one thing about estar, remember that it is used mostly to define temporary conditions.
Changes in meanings
When you use ser with an adjective the meaning of the adjective is often a characteristic or an inherent quality of whatever you are describing. Estar tends to turn the adjective into a condition or temporary state of being. Look at the chart below to see how ser and estar can change the meaning of different adjectives.