Telemetry is a way to collect configuration based tracking data about the installation and the product from Symantec customers. Using telemetry we collect information about how the Symantec customers use the product and the issues that they encounter. This turns out to be an excellent tool to collect the data and understand the customer base that is using this product.
Note Symantec recommends to keep telemetry enabled.
For more information on how Telemetry functionality works and other details, refer attached Telemetry FAQ document.