What is the difference between como esta and estas?

Es is from the verb ser, and esta is (probably) from the verb estar, but the a should be accented.

Ser is used for: Date (May 3rd), Occupation, Characteristics, Time, Origin (you are French or you are from Delaware), and Religion; DOCTOR is the acronym.

Estar is used for: Emotions, Location (you are in the library) and Feelings; ELF is the acronym, and yes it repeats in order to be a proper acronym.

*In other Words, ser= permanent features while estar= constantly changing things. Yes, you can change religion, but usually people don't change their religion every day