Esto es / Este es / Esta es
 

So I know that "esto" is the neutral form of este/esta, but I have the following sentences from Rosetta Stone, and I'm trying to figure out if "esto" must be used or if it can be replaced with "este/esta":






Could I just as well say the following?:

In this case, they can be interchanged.
It depends on what the speaker is thinking about. If they have a more abstract idea of what they're showing, they'll use "esto", but if their conversation partner already has more context or knows what the speaker is talking about, then they'll say "este"/"esta". :)

The neuter pronoun refers to a concept, idea, something already talked about. It doesn't refer to a specific noun.
In your sentences, the demonstrative pronoun appears before the concept (found in the subject complement (predicate noun)). Since the demonstrative doesn't have an antecedent, it must be used in neuter form.

This answers your question, but it doesn't mean that everyone agrees. Generally, if you're not talking about a specific noun (one already mentioned, one you're pointing at, or one that's inferred), the neuter pronoun is usually used.