The Key difference between Ser And Estar is one  of essence and another of condition. In other words, to say what something is, use SER, but to say how something is, use ESTAR, examples:

Sonia es bailarina/ Sonia is a dancer

Pedro está enfermos/Pedro is ill

To tell where something is from, use SER, but to tell where something is located now, use ESTAR, example:

Ana and Pedro are from Spain, but  they are now in Italy/ Ana y Pedro son de España, pero ellos están ahora en Italia.