LDAP is now an Internet standard, covered by requests for comments number RFC1777, RFC1778, and RFC1959, among others. It's supported by many commercial applications, and has a nice Open Source implementation. But first things first. LDAP databases are optimized for looking up entries by name in much the way one would look up an entry in a telephone book. In fact, the most widespread application of LDAP technology is to support electronic address books.
Tags are short codes that follow an accepted convention.
As implied by the existence of the country code, the distinguished name is intended to uniquely identify an object worldwide. The traditional distinguished name, which is derived from the X.500 protocol's convention, uses geopolitical divisions. More recently the LDAP designers have proposed an alternative convention for distinguished names that use Internet domains to ensure uniqueness. Here, a uid containing my email address is used instead of a common name tag. Not only is this type of distinguished name more concise, but it seems more fit for use in our increasingly transnational world.