To get domain validated certificate applicant would need to prove to Certification Authority that he has control over domain for which the certificate is requested. Certification authority will send approval email either to one of generic email addresses, e.g. admin@ webmaster@ and some other, associated with the domain or to email address from domain WhoIs contacts. If applicant is able to receive that email and approve it, then Certification Authority would issue the certificate.
You can also use the alternative validation which requires you to have access to the DNS records of your domain or to the root folder of your website. After the certificate is activated you would need to use the certain CNAME record or .txt file for validation purposes. You can read more information about alternative validation here.This validation procedure is used to ensure internet users that domain holders are who they claim to be. Domain validated certificate will have no information about applicant's company, it will have only domain name for which it has been issued. Here is what you will see in Page Info of site secured by domain validated certificate: Web site: www.yourdomain.com
With domain validated certificate you can place static site seal on your web site to show clients your site is secure and what Certification Authority has issued the certificate for you.