Vulgarity is the quality of being crude and lacking refinement. Fart jokes and swearing are both forms of vulgarity.
One of the criteria used in assessing whether a movie is rated PG-13, R or even X is how much vulgarity in involved. Vulgarity is the quality of being offensive and crass. Fart jokes, sexual humor, and obscenities are all examples of vulgarity. A R-rated movie or TV show on cable likely has some vulgarity. Vulgarity doesn't get much respect because it appeals to people's cruder instincts.