"Ser" is used to describe permanent or essential qualities, characteristics or identities of someone or something. It can also be used to talk about professions or occupations.
For example:
- Yo soy una maestra. (I am a teacher.)
- El es un medico. (He is a doctor.)
- El carro es azul. (The car is blue.)
- Maria es inteligente. (Maria is intelligent.)
"Estar" is used to describe temporary states, emotions, locations, or conditions. It can also be used to talk about actions that are happening at the present moment.
For example:
- Estoy feliz. (I am happy.)
- El carro esta en el garaje. (The car is in the garage.)
- El esta estudiando. (He is studying.)
- El perro esta ladrando. (The dog is barking.)