Yesterday's conjugation of 'ser' ('to be') was only half the story. You don't have to study Spanish for long before you realise that there are two words for 'to be' in Spanish, and figuring out which one to use in a given situation can be pretty tricky for an English speaker. The other verb for 'to be' is 'estar' which we will cover in more detail next week. In general, 'ser' is used for more pernanent things and characteristics whilst 'estar' is used for more transient things, as well as for locations.
I will give a few examples here, and a few more with next week's post to help give you the idea.
soy inglés = I am English
es rubia = she is blonde
es alto = he is tall
las montañas son altas = the mountains are tall
somos profesores = we are teachers
eres muy inteligente = you are very clever