What does c'est moi mean?

Answer 1

It means "It's me" in French

Note that "It's me" is considered non-formal grammar in English (you'd never say "Me am it" but it is quite alright in French since the French Academy approved it).

"It's I. or It is I." is the approved translation.

As previously noted, in proper English the pronoun should match the subject in both number and case. "It" is the subject in nominative case...the pronoun in apposition is required to be "I". To test this, turn it around. "It is I" is equivalent to "I am it."

In English:

Who's talking?

It's I. (I am talking. or It is I who is talking.)

In French:

Qui parle?

C'est moi. (Je parle. or C'est moi qui parle.)

One should never say "It is me who is talking." because that is the same as saying "Me is talking."

In French, it is accepted by the Academy to put "moi" in apposition to "it" or "ce". "C'est moi qui parle". I suppose they just gave up trying to argue the point.

In common English, you often hear "It's me." even though it is incorrect.

If you reply "It's me talking." that could be argued to be an elliptical response, the completion of which would be something like "It is me who you hear talking." Notice that the "me" is functioning as a direct object: You(subject) hear(transitive verb) me(direct object). If you don't involve some form of a transitive verb that requires "me" as a direct object, the example fails. Simply announcing your presence "It is me." is one such example that fails.

Answer 2

"C'est moi" is a French phrase that translates to "It's me" in English. It is often used to assert one's identity or presence in a situation.