This URL, http://download.eclipse.org/tools/ptp/updates, provides access to the software repository for the Eclipse Parallel Tools Platform (PTP).

To install PTP you first download Eclipse, and then use a URL probably under this URL, as a software repository to update Eclipse via the "Help > Install New Software..." menu within Eclipse.

See the PTP release notes and installation instructions for more information.

The URL you need depends on your version of Eclipse.