Hola! =) Soy Mexicano and it isn't true that "es que" is used only for low social classes, it's an expression many people use but it's colloquial. You can use "Es que..." before saying an excuse or explanation for example, it's similar in meaning to "it's just that" "it's only" and "because": ¿Por qué llegaste tarde Carlitos??? ; / - ¡ ES QUÉ había mucho tráfico ! =( ¿¿¿¿Y por qué hueles a perfume de mujer??? - ¡ Es qué entré a la tienda y te compré un perfume de Chanel no.5! =D - ¡Oh! Gracias!!! =)) Pero por qué huele tan mal? ; ( - Es que es una imitación barata =P you can use "porque" instead of "es que" You can see all the examples you made are explanations: Es que no sé nadar. Es que hoy no voy a poder. (I think I get the feel of this sentence...) Es que no tengo dinero. I hope it is clear!!! =)

You use it when answer a question like Why don't you go to swim? = ¿Por qué no vas a nadar?

Hello Hailey, The translation of 'es que' in English would be: the thing is that…, it's just that… So you are basically explaining yourself or giving yourself an excuse by adding after it a reason for having to act in a certain way. Your examples: 'The thing is that I don't know how to swim.' ' It is just that I don't have money.'

...vulgar?