What is the Use of Third Wire in 3 Wire RTD?

When resistance between two wires to same end of RTD was measured, from control panel to bearing temperature "100 ohm platinum" RTD, it was found to be 10 ohms. Each wire to RTD was thus 5 ohms. 5 ohms each lead in two wire connection would cause about 25 Celsius error in temperature (high). Three wire connection enables an automatic error compensation circuit to be used to get accurate measurement.