KMSPico Activator works by emulating a Key Management Service (KMS) host. When a user installs Microsoft Office 2021, it requires activation to unlock all the features. KMSPico Activator creates a virtual KMS host on the user's computer, which tricks Office 2021 into thinking it's a legitimate KMS host. This allows Office 2021 to activate and use all the features without requiring a genuine product key.