Dfferential Pressure Feedback Exhaust or sometimes in the US it is reffered to as Delta Pressure Feedback EGR.
It is a sensor used to monitor the EGR flow by sensing the difference in pressure between the 2 vacuum/pressure pipes attached to it. From this it can establish whether correct EGR flow is taking place or if there is a restriction etc. Internally I guess it's like a double MAP sensor.
There is a restriction in the metal EGR carier pipe with a vacuum pipe on either side connected to the DPFE so the sensor can read exhaust pressure and know that the EGR valve is operating when the pressure on either side of the restriction changes differently. ECU then knows EGR is flowing. My first experience of these was on the first generation Mondeos, it was mounted on the bulkhead. Think I've only ever seen it on Ford and Mazda products.