An instance of AD LDS is a single running copy of AD LDS. Unlike Active Directory Domain Services, multiple copies of AD ...

An instance of AD LDS is a single running copy of AD LDS. Unlike Active Directory Domain Services, multiple copies of AD LDS can run simultaneously on the same computer. This improves availability and load balancing when instances are replicated across multiple servers. Each instance of AD LDS has a separate directory, a unique service name, and a unique service description that is assigned when the instance is created.