What is the difference between section and sub-sections in academic reading terms?

Answer 1

A section is a bigger grouping; sub-section would come under it. So your section might be "animals" and your sub-sections might be mammals, reptiles, amphibians, etc. Or if the section were Presidents, the sub-sections could be the various Presidents, or they could be "Presidents from the beginning of the country until 1850", "1850-1900", etc.