The Titania sensor looks very similar to the Zirconia type, although it is normally smaller. The fundamental difference between the two is that unlike the Zirconia sensor, the Titania type is not able to generate a voltage and requires a base voltage to be supplied by the ECU.
The sensor is made from a titanium dioxide ceramic element which changes electrical resistance in response to the concentration of oxygen in the exhaust gas. The ECU measures this signal and adjusts the fuel feed in response. If the fuel mixture is rich, the resistance will measure low. An oxygen rich, or lean mixture, will have a high resistance measure.