VMware’s auto-deploy have two options for ESXi hosts provisioning. This feature was introduced in vSphere 5.1.
Stateless installation option will cache the ESXi host image locally,
Stateful installation is used when you want to install the host from Auto-Deploy. After the initial installation, every time the host boots it will boot like any other host that you installed manually.
Please refer to this links for further information about Auto-Deploy and Stateless vs Stateful installations:
Mastering VMware vSphere 6, Page 39