When you invite someone to your home for the first time, you have to tell them how to find you. The easiest way to do this would be to simply give them your address. From there they can navigate directly to your home.
Similarly, a domain is your website's address. It’s how visitors will find their way to your website. Selecting your domain is an important step, as not only will it affect how easily your customers find you, but it can also help improve SEO for your brand.