From the article:
There are two important concepts for users: authentication, and accounts. With Active Directory authentication uses the Kerberos 5 protocol, and account information uses LDAP. Therefore we need to configure Kerberos 5 and LDAP on Ubuntu in order to manage users in an Active Directory.
This article is written specific to configuration against a Samba 4 Active Directory as part of the directory server
There is also offical Microsoft Active Directory support tutorial at the Ubuntu Wiki called Active Directory Howto.