The suffix is the name of the entry at the root of the DIT. If you have two or more DITs that do not have a natural common root, you can use multiple suffixes. The default Directory Server installation contains multiple suffixes. One suffix is used to store user data. The other suffixes are for data that is needed by internal directory operations, such as configuration information and directory schema.
All directory entries must be located below a common base entry, the suffix. Each suffix name must be as follows:
Static, so that the name rarely changes
Short, so that entries beneath the suffix are easier to read online
Easy for a person to type and remember
It is generally considered best practice to map your enterprise domain name to a Distinguished Name (DN). For example, an enterprise with the domain name example.com would use a DN of dc=example,dc=com.