"Este" is masculine. Examples:
Este carro. This car
Este trabajo. This job
Este dormitorio. This bedroom
Este trabajador.. This worker
"Esta" is feminine. Examples:
Esta mujer. This woman
Esta doctora. This female doctor.
The word "esto" Using when the sentence have no gender or is undefined. Examples:
Yo no quiero esto. I don't want this.
Esto es malo. This is bad.
Necesitamos trabajar para esto. We need to work for this.