This is soil moisture sensor module. PCB based small but effective probe and complete module with connecting wires. Two pads of probe acts as variable resistance as more water means better conductivity and resistance reduce and high output. Just connect vcc and gnd in module and it will give two output one is analog another is digital.
Trim pot in the module is used for threshold setting for moisture level sensing, digital will give high or low depending upon level set for amount of moisture. Analog pin will be used for controller or Arduino ADC pin to determine the moisture level.