A domain name is a unique address or identifier on the World Wide Web that separates you from everyone else. One recognizable example is 'google.com'. Type that domain name in your browser's address bar and the worldwide system of name servers connects your computer to Google's web site.
Your domain name is the first thing people see when they find your website. Your web address is the first impression about you or your organization. Having the right domain name is critical to giving a positive first impression, no matter what your website does.