...
We provide a range of different "variants" of each Windows version, and they are named with the following keywords:
...
Evaluation
This is the Evaluation version of Windows. The evaluation period is 90 days for Client SKUs and 180 days for server SKUs. When the evaluation period has run out, Windows will automatically shut down a short while after you boot it. An evaluation period can be restarted "a few" (varies for every SKU) time, by issuing the command slmgr.vbs /rearm in a command prompt ran as admin.
...