Estar is used to describe temporary states like how you are feeling (tired, happy, sad), while ser is used to describe permanent traits. Some examples of estar include "Yo estoy muy bien" (I am very well) and "Ella está deprimida" (She is depressed). Ir is used to talk about where you are going or future plans, using constructions like ir a + place or ir a + verb. Examples include "Yo voy a la biblioteca" (I am going to the library) and "Ellos van a escuchar música" (They are going to listen to music). Questions about where someone is going use "¿A dónde...?"