Esto is the neuteral form of este, which is masculine.
In Spanish, neuteral pronouns are used to refer to something that has just been mentioned or that is about to be said, and also to ask or talk about statements, ideas, and vague or unnamed things.
Decir eso es tanto como no decir nada.
Nunca olvides esto: tu familia siempre te apoyará.
¿Qué es aquello que se ve detrás de las montañas?