To be - Ser and Estar in Spanish

In Spanish "Ser" and "Estar" both mean "to be". But they are used in different situations. Here is an overview.

Ser

Ser is used to describe permanent states, or states that rarely change. This includes:

• Profession, nationality, origin or religion of people
  
• Characteristics of people or things, like size, color or material.
  
• Description of time (time may change but Wednesday remains Wednesday)
  
• Belongings of people or relationship between people
  
• Personal preferences or hobbies
  

Examples:

Juan es un amigo sincero. (Juan is a sincere friend.)
Soy fanático de la musica rock. (I am a big fan of rock music)
¿Eres amiga de Pedro? (Are you a friend of Pedro?)
El sol es el centro del sistema solar. (The sun is the center of the solar system.)
Pablo es profesor de física. (Pablo is a Physics teacher.)
Mi hijo es bajo para su edad. (My son is short for his age.)
Ese perro es peligroso. (That dog is dangerous.)
Marta es una buena persona. (Marta is a good person.)

Estar

Estar is used to describe a temporary state that may change or positions. This includes:

• Location or position
  
• Feelings of a person
  
• Ongoing actions (i.e. with the present participle, "he is cleaning")
  
• Characteristics of an object or a person that may change
  

Examples:

Todavía no estoy pronta para salir. (I am not ready to leave yet.)
Alicia está vestida de rojo. (Alice is dressed in red.)
Estoy paseando por París. (I am strolling through Paris.)
El bebé está durmiendo la siesta. (The baby is taking a nap.)
¡Estás preciosa con ese vestido azul! (You are beautiful in that blue dress!)
Estoy mirando un nuevo programa de televisión. (I am watching a new television show.)