It will disable a lot of the Windows 10 telemetry features. Those are the features that send a bunch of data about your usage back to Microsoft. This includes Cortana and the Bing search tool in the normal windows search for example.

If you want to run it you should read through it first, it says above every function what it is going to disable. I would go with a simple rule: If you don't understand it, don't disable it. Otherwise it contains code for enabling all features again in case you start to miss something.

Edit: especially UI part seems to disable a lot of things by default that you might not want to disable!