While both ser and estar can translate to to be in English, they aren't interchangeable in Spanish.
Ser is used to classify and identify permanent or lasting attributes.
Estar is used to indicate temporary states and locations.
If this general rule is too vague for you, think of the acronym DOT. Ser is used for:
Descriptions of a person or thing.
Origins of a person or thing.
Time.
In this article we'll take a look at the D in DOT: descriptions. Let's get started!
Descriptions with Ser
Ser is used for all permanent/long-term and personal descriptions. You can use ser to answer the question How would you describe __?
In other words, ser is used with the essential qualities that define a person or thing and that are not likely to change in the near future. These can be names, physical descriptions, occupations, personal relationships, and religion, among others.
Names
Soy Raúl.
I am Raúl.
Son Adela y Amalia.
They are Adela and Amalia.
Physical Descriptions
Soy alta y delgada.
I am tall and thin.
Silvia es pelirroja y baja.
Silvia is red-headed and short.
Occupations
Soy profesora de español.
I am a Spanish teacher.
Son jardineros.
They are gardeners.
Personal Relationships
Anita es mi hermana.
Anita is my sister.
Aaron es su prometido.
Aaron is her fiancé.
Religion
Juan es católico.
Juan is Catholic.
Mis padres son budistas.
My parents are Buddhists.