Odoo has many enterprise social features. It performs many activities online such as sending email, inviting your customers to a portal and sending a document to get it signed online. All these activities bring users or visitors to your instance. By default, Odoo assigns a sub-domain name based on your company name filled-in at the time of creating an Odoo instance: https://yourcompany.odoo.com.
Odoo allows you to personalize your instance, you can set up your personal domain name and website theme on the online instance. Once a visitor accesses your website by typing your company's domain name, https://yourcompany.com, they are immediately redirected to your instance.