Reading comprehention.

There are three important things that you can identify in a text. Three things are:

• Theme; the genereal idea that the text is about. Love, sadness surprise, etc.
• Topic; particular idea of the text. "Sadness of Tom, for losing his father".
• Main idea; is the  the message that the author want´s to give to the audience.

Source, audience, purpose, genre, tone, register, etc. Are other types of things you can find.