After you purchase vSphere licenses, VMware provides a serial number that you use to license ESXi hosts. You can use evaluation mode to explore the entire set of features that are available for ESXi hosts, including features that are not included in the license that you have.

For example, in evaluation mode, you can use vMotion, HA, DRS, and other features, even if you have not licensed those features.

The installable version of ESXi is always installed in evaluation mode. ESXi Embedded is preinstalled on an internal USB device by your hardware vendor. It might be in evaluation mode or prelicensed.

The evaluation period is 60 days and begins when you turn on the ESXi host, even if you start in licensed mode rather than evaluation mode. Any time during the 60-day evaluation period, you can convert from licensed mode to evaluation mode. To take full advantage of the 60-day evaluation period, you should convert to evaluation mode as soon as possible after you first power on the host.

For information about managing licensing and setting an ESXi host to evaluation mode, see the vCenter Server and Host Management documentation.