First SSL Certificates can be broken into 3 validation types, being domain validation, organisation/business validation and extended validation. Validation is the process you will need to go through to be issued a certificate, each type comes with certain features.
Domain Validation
Being the most widely used SSL Certificate available, Domain Validation Certificates are also the most easy to order and setup. As they do not require you to be a registered business entity and submit paper work.
Validation of domain ownership is acquired through a link you need to click on being emailed to an email address associated with the domain, such as admin@yourdomain.com or webmaster@yourdomain.com. Alternative validation methods do exist for some Certificate Authorities such as Comodo which include uploading a file to your website root or creating a CNAME record under your domain.
You can generally get a domain validated SSL Certificated issued within 3 to 10 minutes. You may obtain Single Domain, Multi Domain (UCC/SAN) and Wildcard ( unlimited sub domains ) Certificates through domain validation. Although they are completely secure and browser trusted certificates they don’t offer the same amount of trust given to customers as other validation types.
Business Validation
Also named Organisation Validation, these SSL Certificates give your customer an extra level of trust due to the requirements of you being a registered business entity in your country. When your certificate is ordered the Certificate Authority will request paper work of your business details which include your business number ( ABN for Australians ) business address and the person in charge. Most Certificate Authorities will also required phone validation.
When your certificate is installed on your website your business details will be visible when anyone inspected the certificate. This helps to give your users that extra level of trust not obtained from a domain validated certificate because your business details have been confirmed and validated, and no one else will be able to generate a valid certificate with these details. Helping to protect your customers again Phishing ( another website pretending to be you ).
Business Validation SSL Certificates generally take between 3 to 7 days to be ordered and issued. You may obtain Single Domain, Multi Domain (UCC/SAN), Wildcard ( unlimited sub domains ) and Server Gated Cryptography Certificates through business validation.
Extended Validation
Extended Validation SSL Certificates offer your customers the highest level of trust while displaying the green address bar in your visitors browsers.
You will be required to be a registered business entity for Extended Validation Certificates and supply documentation to the Certificate Authority. When your certificate is ordered you will be required to go through extra steps for validation which include a phone call to the business listed phone number, signing of official documentation and supplying registered business details. When you have installed your EV Certificate and visitors browse to your website, their browser address bar will change to a green colour to show that the visiting website has gone through extended business validation.
When your visitors click on the lock icon in the browser they will be presented with the Certificate details including your business details including your registered business name and address. This all helps to prevent anyone else to fake your business ( Phishing ) and give customer total trust in your business.
EV SSL Certificates generally take between 5 to 10 business to be issued from your order. You may obtain Single Domain, Multi Domain (UCC/SAN), Wildcard ( unlimited sub domains ) and Server Gated Cryptography Certificates through Extended Validation.
With certificates broken into the 3 validation types mentioned above they can now be broken down into 4 different types including Single Domain, Multi Domain (UCC/SAN), Wildcard ( unlimited sub domains ) and Server Gated Cryptography Certificates
Single Domain
Single Domain SSL Certificates secure a single domain name such as www.mydomain.com, mail.mydomain.com or mydomain.com. A large amount of Single Domain Certificates will include the root domain when you order the certificate with the including www. ( so you get www.mydomain.com and mydomain.com secured ).
If your have a single domain certificate for www.mydomain.com and you setup a new subdomain mail.mydomain.com the certificate will not work for that new sub domain, you will need to either purchase a new certificate or change to a another type such as a Wildcard or Multi Domain Certificate
Wildcard
A Wildcard SSL Certificate allows you to secure an unlimited amount of subdomains. So you could secure www.mydomain.com. mail.mydomain.com, www2.mydomain.com and mydomain.com. This will help save money if you are required to have customers visit more then one of your websites under your domain name with different sub domains. Wildcard Certificates will be presented like *.mydomain.com
Multi Domain (UCC/SAN)
Multi Domain SSL Certificates allow you to secure more then one domain name. Also named Subject Alternative Name (SAN) or Unified Communication Certificates (UCC). You could secure www.mydomain.com, www.mydomain.com.au, www.myotherdomain.com or mail.mydomain.com all with a single Certificate. These Certificates are often used to secure Microsoft Exchange 2007 Server, Office Communications Server 2007, or Mobile Device Manager.