This is a stainless steel, Type-K Thermocouple probe. A thermocouple works by taking two wires made of dissimilar metals, connecting them at the two ends, and making a temperature gradient between one end and the other (a ‘hot’ end and a ‘cold’ one). Once this is achieved, a voltage potential is formed and current flows. One junction is held in the environment where the temperature of interest exists, this is known as the hot junction. The other junction, referred to as the cold junction, can typically be found in ICs that specialize in reading the temperatures detected by the thermocouple probe.