By using LDAP filters, criteria can be specified when searching for certain objects within the directory. Nontechnically spoken, criteria for LDAP filters could be:
You will need such filters in LEX whenever you want to search the directory for objects with a complex search operation, or when you want to filter the object list in the LEX main window.
LDAP filters are basically text strings with a special syntax. There is a special online manual topic about the LDAP Filter Syntax.
Because LDAP filters can be quite complex but are important for daily directory operations, LEX comes with a tool where you can store and construct filters: The LEX Filter Factory.
This Filter Factory has a Filter Constructor which allows you to handle the logical structure of a filter - and an Single Filter Editor dialog.
Last but nor least: LEX comes with quite a lot of pre-defined 'famous' LDAP Filters which helps you understand and use the LDAP filter syntax for your own searches.
Because LDAP filters are needed in many situations, you can even use LEX and it's ability to build and construct LDAP filters or to display the logical structure of complex filter strings to use the results in other applications - for example in the Active Directory Users and Computers tool for the Saved Queries dialog: