The genitals or sexual organs are the reproductive organs in most humanoid species. In the Human species, the males and females have different sexual organs. (TNG: "The Outcast")
The fact that different humanoid species can interbreed implies that most humanoids have distinct male and female sexual organs. A notable exception are the J'naii.
In males, the testes are very sensitive to pressure. A sharp blow to the organ can render Humans and aliens helpless.
In at least one species, the genitals are located in the right knee. This is different from many other species. This did not however, affect the sensitivity of the organ. (Star Trek VI: The Undiscovered Country)
Jadzia Dax had her ovaries operated on in an attempt to be able to conceive with Worf. (DS9: "Tears of the Prophets")