the bridge in question is a wheatstone bridge.

a full bridge is, practically speaking, two potentiometers composed of four individual sensors. if you had a full bridge gage, R1 & R2 would effectively be one potentiometer, and R3 & Rx would be a different potentiometer. all four resistors would be variable resistors that respond to what the gage measures. they would be arranged so all four contribute to the output: An increse in what the gage measures would cause R1 & Rx to decrease resistance while R2 & R3 increse resistance.
R1 * Rx should equal R2 * R3. if they are more than 2% different, one of these resistors will carry current, get hot, change value as it heats, and the baseline of the gage will drift.
the wheatstone bridge illustrated here is a quarter wave bridge, only one active element.
you will get an analog value between C and D. if one leg of the power source is grounded this will be floating, not referenced to ground. you read this with an analog input pin, which is referenced to ground
you need to research how people get around this. If you can use a battery for the excite voltage, or a power supply with a floating ground ( a wall wart that does not have a connection between the negative lead and ground ) you can ground C or D and measure the resulting voltage