A domain name is the unique name that each website has.
If you think of your website as a building, then the domain name is its street address. Your domain is the place people need to go to visit your website, and each domain is completely unique.
From a technical side of things, a domain name makes it easier to browse the internet and access a specific website. Instead of having to use an IP address, (which is a convoluted string of numbers and letters computers use to recognize a website), a domain name is a simpler combination of letters, numbers and symbols someone types in their browser to access a specific web address directly.
For example, if you wanted to visit GoDaddy’s website, it’s not enough to just type “GoDaddy” in your browser — that would simply provide you search results for “GoDaddy” and would not render the actual website. Instead, you need to type the domain name “GoDaddy.com” in the browser to navigate to GoDaddy’s website.