What is the difference between site owner & site collection administrator?

We are going a give a look about site collection admin and site owner roles and difference between.

First of all we need to understand about what is site collection and Site owner:

Site Collections: From the TechNet and Office 365 Blogs,

A Microsoft SharePoint online or on premises site collection is a top-level (or root) site that contains subsites. SharePoint Site Collection.

SharePoint Site a SharePoint intranet or intranet portal is a way to centralize access to enterprise information and applications. Is a website that contains different SharePoint Web Parts like Document Library, Calendar, Task List, etc. SharePoint sites can have 1 or more pages to display content to the user.

See more from below link:

https://technet.microsoft.com/en-us/library/cc262410.aspx

Site collections: Below screen will appear will be for  site setting on site collection page.

Site owner:  Below screen would be appear for subsite site setting

Thanks