SAN certificate (Subject Alternative Name), we refer to an SSL certificate that has the ability to protect several domains in a one certificate, also called a multiple domain SSL certificate. The SSL SAN certificate offers the same encryption as normal SSL but protects several host names.
The SAN certificate allows you to protect a primary domain and add others to the SAN field of the certificate.
For example,
www . your-domain . com
mail . your-domain . com
www . your-domain . net
www . your-new-domain . net