A page is the first part of an application that you will create. This is generally used for a broad area of data, such as "Personal information," under which several other sections fall (in this case, contact information, current address, permanent address, contact information, and name all fall under the broader umbrella of "personal information").
Sections are sets of questions, typically arranged together to gain a specific type of information. In the section labeled "Contact information" under the page "Personal information," you can anticipate questions that ask for phone number, email, fax, website, facebook, and so on.
To summarize, questions ask specific things. They are organized into sections that gain a specific type of data, and that data makes up the larger umbrella defined by pages.