This is a force-sensitive resistor with a square, 1.5" x 1.5″ sensing area. This FSR resistance varies depending on how much pressure is applied on the sensing area.

The harder the force, the lower the resistance. When no pressure is applied to the FSR its resistance will be larger than 1MΩ. This FSR can sense applied force anywhere in the range of 100g-10kgs.

Two pins extend from the bottom of the sensor with 0.1″ pitch making it breadboard-friendly. There is a peel-and-stick rubber backing on the other side of the sensing area to mount the FSR.

Just connect a resistor to form a voltage divider and measure the voltage at the junction (across the FSR) to find the force applied.

These sensors are simple to set up and great for sensing mechanical pressure, but they aren’t incredibly accurate. Use them to sense adhoc pressures applied (presence of it), but you may not want to use it as a reference scale. 

This sensor can be easily interfaced with Microcontrollers boards viz. Arduino Boards, Raspberry Pi etc. using an Analog to Digital Converter (ADC).