What's "it" in "that's it" mean here?
Native speaker’s answer
Rebecca
"That's it" is an expression, so the "it" doesn't really mean anything on its own. The expression has the same meaning as "Is that all/everything?" to ask if the whole situation or event was described and if there are any other important details? "That's it?" implies that the speaker hopes there isn't anything more. It's usually followed by a statement that is used a question, to confirm is "that" (everything that has happened or been described) is "it" (the information is complete and there is no additional information). "Is that it?" is more neutral, and the speaker is asking if there is more with less emotions attached. Ex: What you told me about the conference call, is that it, or is there more? Ex: So, that's it? We're done with the project?
