The LDAP specification allows the use of attribute options. Attribute options can provide metadata about values for the attribute. Multiple options can be provided for a given attribute/value.

The classic example is language. displayName;lang-en tells you that this is the English version of displayName. displayName;lang-jp would be the Japanese version.

displayName;lang-en: Hideki Matsui
displayName;lang-jp: 松井秀喜

Generally, options behave intuitively. A query without specifying an option should match all relevant attributes (ie: displayName matches both displayName;lang-en and displayName;lang-jp), while a more specific query matches only relevant attributes (so displayName;lang-fr would not match either of the above examples).