In simple words, this means that when the plugin is enabled Freespee will feed information about calls to the customer DoubleClick Search account. In the feed, there will be information linking each call to the DoubleClick Search visitor and the particular ad that generated the conversion. The Freespee DS plugin utilises the DoubleClick Search Conversion API and feeds data to the customers DS account in real time. Bid strategies in the DoubleClick Search platform will be able to leverage this data and make better mathematical bid decisions based on more complete statistics (rather than partial statistics which will be the case of not accounting for call conversions).
In the Freespee platform, when activating the plugin, you can choose which Action Tag in the DoubleClick Search platform to attribute calls to. For example, you can choose to send calls that are considered successful (dependent on your selected call qualification criteria in the Freespee platform) to one Action Tag and all other calls to another Action Tag.