The GeForce Experience in-game overlay enables you to access GPU-accelerated video recording, screen-shot capture, broadcasting, and cooperative gameplay capabilities. If you do not intend to use these features on a particular PC, you may disable SHARE by following the instructions below:
1) From the GeForce Experience app, click in the Settings icon on the top right corner:
2) From the General panel, toggle the SHARE setting to off as shown in the screenshot below.
Note: If you wish to use GeForce Experience SHARE again, you may simply enable the SHARE toggle to on.