Introduction to site collections

Site collections and site hierarchies have been part of the SharePoint experience for quite some time, and those structural components continue to be available in SharePoint Online. However, SharePoint Online features one new structural paradigm that doesn't really exist fully on-premises: the hub site. As such, we can divide SharePoint architecture generally into two categories: classic and modern.

Classic SharePoint

The classic architecture is what we're familiar with; it has a curated look and feel and is typically static. Classic sites and site collections are built using a wide range of specialized templates, grouped into three families (Collaboration, Enterprise, and Publishing...