From RFC2253:

• CN - common name (commonName).
• OU - organizational unit (organizationalUnitName).
• DC - domain component (domainComponent).

these are the most common attribute types found in an LDAP query string.

LDAP is based on a hierarchical tree structure where a query string such as:

cn=Dev-India,ou=Distribution Groups,dc=gp,dc=gl,dc=google,dc=com

is read from right to left, where right-most represents the top of the tree and the left represents a leaf.

For the example above, the query string references the Dev-India leaf found at the bottom of the tree: