Since we're talking about ТО ЧТО, I'd like to point out that there's another possible translation. In some cases ТО ЧТО can mean "the fact that". Usually context indicates which translation makes sense, but not always. I think the example Мы говорили о том, что вы читали. can mean either We talked about what you read. or We talked about the fact that you read.

Feel free to correct my mistakes.
Будьте вольны исправлять мои ошибки.