Your domain settings is the text that appears in your documents URLs. Since all of your clients documents are accessible via weblink, these links will have a website address associated with them. It will be important that you change this so that your URLs can appear more representative of your brand/business.
Under "Account Settings", and "Brand Preferences", you will notice a field called "Subdomain". By default it will show a random string of numbers.
Keyword Search: Domain, Numbers, Subdomain