Domain Name is simple idenity which when uses types on a web browser will get the infomation that you want to share. So domain name in lay maen terms is your website name. When ever people type you domain name they will get access to your website or webpages.
Domain name looks like
www = World Wide Web
You name = the name you choose as your website name or online idenity.
Domain extenstion = .com, .net, and many more domain extenstions are avalible.
Domain name is one of the starting part to create a online webiste. You need to get a domain name that you can share as your website or blog.