Hello Kommb!:) Well, "ser" is for states, things you cannot change. Like being Japanese, being a mother, being a man, being a student, etc... • Soy japonés. • Soy el hermano de Sarah. "Estar" is for temporary states, things that can change in a certain amount of time. Like beign ill (if you take your medicine, you'll be healthy again), being in an office/school/house (you can get out of there to go somewhere else), etc.... • Estoy en el trabajo. • Estoy con mi hermano. For example: "Él está enfermo" means that now/for the time being/these days that man is ill. He wasn't ill before, and he probably will be cured soon. "Él es un enfermo" means that he probably is a psychiatric patient or that he is mentally disturbes. He has probably had allways had a mental problem, and it's very likely that he won't get cured. I hope that this was helpful:)