A thermocouple is made up of two dissimilar metal wires. Dissimilar is just a fancy way of saying Different, but for some unknown reason, that word tends to be used most of the time when discussing thermocouples.
In any case, the metal wires are connected together in only one place, typically the tip of the thermocouple. Lots of manufacturers call that junction by different names. Hot Junction, Measurement Junction, Sensing Point, or Sensing Junction. Those terms all refer to the same thing… the place where the dissimilar metals are joined that will measure the temperature.