Hola! Both of these verbs mean “to be”, but we can’t use them interchangeably. It is very important for you to understand and be able to differentiate them.
Yo soy Nosotros somos
Tú eres Vosotros sois
Él/Ella es Ellos/Ellas son
The first verb, “Ser”, means “to be” in a way in which you can put an equal sign between a verb and a noun.
It refers to things that are invariable, not temporary, for example:
Soy Polaco I’m Polish (I am, and I always will be, it won’t change)
Este bolígrafo es verde this pen is green (and will always be)
Clara es alto Clara is tall (and it isn’t likely to change)
Juan es católico Juan is a Catholic
Este casa es tuyo This house is yours
But, of course, there are exceptions, for example with dates or places where something is happening:
Hoy es lunes Today is Monday
La fiesta es en mi casa The party is at my house
Yo estoy Nosotros estamos
Tú estás Vosotros estáis
Él/Ella está Ellos/Ellas están
The second verb also with, as I said, meaning “to be”, refers to things that are temporary,
¿Dónde estás? Where are you? (now you are here, but in five minutes you’ll be in some different place)
¿Cómo estás? How are you? (at this moment, later your mood will change)
Luis está felíz Luis is happy (in this moment)
And when we’re talking about the location (but not that something is taking place somewhere)
Lodres está en Inglaterra London is in England
Mi oficina está en el centro my office is in center
Of course, it’s not all, it couldn’t be this easy :) There are some expressions that have different meanings, depends on which verb you use. Some of them are phrasal verbs, so it’s very good to know them and use in daily language.
Here is the list of them:
BUENO/A
•ser: someone honest
•estar:
a) to be tasty (este pastel está buena this cake is tasty)
b) to be attractive, looking pretty at some particular moment (estás buena en este vestido you look beautiful in this dress)
LISTO/A
•ser: to be clever, intelligent (Ana es my lista, siempre sabe que decir Ana is very intelligent, she always knows what to say)
•estar: to be ready be (¿estáis listos? are you ready?)
VERDE
•ser: to be green, as a colour ( este bolígrafo es verde this pen is green)
•estar:
a) to be unripe (esta manzana está verde this apple is unripe)
b) not to be experienced (Julia está verde en gramatica española Julia isn’t good in Spanish gramatic)
MALO/A
•ser: to be bad (evil), have bad character (No puedes hacerlo, no eres malo you can’t do it, you’re not evil)
•estar:
a) to be ill (Clara no puede reunirse, está mala Clara can’t meet with us, she’s ill)
b) to be distasteful (esta comida está mala this meal isn't tasty)
ABIERTO/A
•ser: to be an extravert, someone sociable and tolerant (Tienen muchos amigos, son muy abiertos they have many friends, they are open to people)
•estar: be open, not to be closed (Esta tienda está abierta this shop is closed)
RICO/A
•ser: to be rich (La familia de Luisa es rica, salen al extranjero cada año Luisa’s family is rich, they go abroad every year)
•estar: to be tasty (Tus platos están ricos your meals are delicious)
I think it would be all that you need to know :) Remember, learning a new language is just like trying any new thing for the first time - the more practice the better. Good luck!