Domain – The name of the website that people type into a browser to visit it. For example, my domain is monicamorgandesigns.com.
Registrar – The company used to register your domain name. Some examples include GoDaddy or Network Solutions.
Hosting – Certain computers, called “servers” are used to house all the files that make up your website. They “serve” the content to various devices (desktops, laptops, mobile phones, etc.) when the domain is requested.