How to build a web page using different sections created in Craft
Actually, not all sections are created equal. Craft actually has three different types of sections:

Singles
Channels
Structures

Well, you need to work with dynamic URLs and Twig to show your sections at Web Page.
Here is the link of official documentation of Craft CMS:
https://craftcms.com/docs/2.x/sections-and-entries.html#sections