like larry said, the verb "to be" has to different meanings in spanish, either "ser" (yo soy, tu eres, él/ella/eso es, nosotros somos, ustedes son) or "estar" (yo estoy, tu estás, él/ella/eso está, nosotros estamos, ustedes están) although in some cases they are very similar, that's why they are kind of tricky and difficult to explain and understand.
The difference i'd say is matter of time and general speaking. For example, for describing yourself, your physical appearance, your behavior, your attitudes, qualities, your career, your job. You should use the conjugation of "ser" so you may say:
Yo(subject is optional) "soy" atractivo (i'm a good looking guy), soy divertido (funny), soy entusiasta (enthusiatic), soy un poco flojo (i'm kind of lazy), soy economista (economist), soy empleado/trabajador (employee, worker), that is for daily basis, a routine, something that you always are.
For speaking in specific moments or situations we use "estar" ,so maybe i had a horrible day and i can say, I'm sad (Estoy triste), I'm tired (Estoy cansado), that doesn't mean that's my normal behavior, the way i usually am. another example could be that by the time i'm working at samsung company, maybe in the future i'm going to be working somewhere else or i worked for pepsi company before entering samsung. so I could say: I'm working at samsung before that i was working for pepsi co. ("Estoy" trabajando en samsung, antes de eso "estuve" trabajando para pepsi)
so that's the way I see it as a spanish speaker, i'm not a teacher, but i hope this had been helpful for you. greetings from Mexico!!