1) The basis for a SP is the SITE COLLECTION:

 For example https://keminind.sharepoint.com/sites/KAE

2) Within a SITE COLLECTION you can have (SUB) SITES

   1.1. https://keminind.sharepoint.com/sites/KAE/Sales

   1.2. https://keminind.sharepoint.com/sites/KAE/mrktg 

3) Within a SITE you can have again (SUB) SITES

   1.2. https://keminind.sharepoint.com/sites/KAE/mrktg/MonRpts/ 


4) Within a SITE (also within a SITE COLLECTION) you can create CONTENT

    4.1.  PAGES

    4.2.  LIBRARIES

    4.3.  LISTS



a PAGE always contains SitePages in the URL ==> https://keminind.sharepoint.com/sites/KAE/Sales/SitePages/Monthly-Sales-Report.aspx

a LIST contains /Lists/ and an additional list name in the URL ==> https://keminind.sharepoint.com/sites/KAE/mrktg/Lists/ListName

a LIBRARY contains an additional library name in the URL ==> https://keminind.sharepoint.com/sites/KAE/mrktg/MonRpts

Owners can create a Document Library by going to the Site Content (page) and select "New" and "Document library"


If you want to add metadata columns to the new document library, you can do this using the Add Column drop-down.