I agree with everyone else, but I think there is another difference with the two words (and maybe someone already mentioned this)
"Este" is a demonstrative adjective (adjetivo demonstrativo), because it describes a noun. Este libro...This book.
On the other hand, the word "éste" with the accent is a pronoun, because it takes the place of the noun. For example, Me gusta este libro, pero no me gusta ÉSTE.
The same goes for femenine words. Esta - Demonstrative adjective; Ésta - pronoun
Me gusta esta copa, pero ésta es fea.
You use "esto" when you're referring to something that has no gender...it's called a Demonstrative pronoun (neuter form). You use it when you're talking about something that is just an idea that really doesn't have a masculine or femenine word to put to it.
For example, "Esto no es normal" (This isn't normal...the word this is neuter because you don't know for sure what "isn't normal")
Neuter forms are:
Esto - This
Eso - That
Aquello - That (not exactly sure the difference between this and "eso" is...sorry i'm not a native speaker just an eager spanish student!)
I hope that makes sense to you...if not message me and I can try and give you better examples.
Suerte!