OpenLDAP is an open-source implementation of the Lightweight Directory Access Protocol (LDAP), which is used for accessing and managing directory information. It allows organizations to store user and resource information in a centralized database, making it easier to manage access and authentication across various applications and services. With OpenLDAP, administrators can create, modify, and query directory entries, which can include user accounts, groups, and other resources. It supports various authentication methods and can be integrated with other systems, enhancing security and streamlining user management in both small and large environments.