Manufactured by Spectra Symbol, these are small strip controllers with adhesive backing, also known as 'soft potentiometers'.
There is a nominal 10K resistance at two outer ends. The resistance in the middle pin varies depending on where it is pressed on the strip. When no pressure is applied, the middle pin floats, so make sure to use a kind of weak pull, like 100K ohms.
To use, connect one side pin to ground via a 10K resistor in series, and connect the other side pin in series to a different 10K resistor to your Vcc power line (3V, 5V, etc.). Then read the analog voltage on the middle pin. It will vary between 1/3 Vcc and 2/3 Vcc. Do not connect directly to Ground and Power.
You can order the Linear SoftPot (Strip Sensor) from the Adafruit category at SAMM Market at a reasonable price, with same-day shipping and fast delivery advantages.