What is required system or functions for most of the websites?

I’m doing a research about the the most required systems or functions for most of the websites (e-commerce, blog, personal, portfolio, etc.) . Such as, Login & Registration System, Dashboard, CMS, Shopping Cart (e-commerce), Search System, etc.

Because I want to work on a base of systems for all types of websites, so if I want to develop any kind of website it becomes easier for me.

Please list any basic systems/functions could help.