Answer:
to explain the main idea of a section.
Step-by-step explanation:
A heading can be defined as a word, phrase or group of words placed at the top of an informative text (write-up) or section of a text as a title.
The main purpose of headings in an informative text is to explain the main idea of a section. This ultimately implies that, a header should be used as a title when an informative text is broken down into sections; each section having a unique and precise function.
Hence, a proper use of a heading in write-ups or books help the author to organize and develop his or her ideas for an effective and clear understanding of the information by the audience (reader).