First, if "esta" is wrong typed, because you're talking about the verb "to be" in spanish, (estar), and conjugated it'd be "está" in this case. "esta" means "this", as you can see it's a really different word, but don't worry, it's not a serious mistake :)
"ser" is used to describe things. For example:
*Yo soy Cristan
*Mi trabajo es horrible
"estar" is used to talk about actions and moods. For example:
*Ellos están jugando al futbol
*En este momento estoy triste
I hope I'd helped you!