Horses' gums recede with age, leading to longer teeth. A common way to inspect a horse's worth is to check it's mouth, hence the phrase. Receiving a horse as a gift and immediately inspecting its value was considered offensive, much like inquiring about the worth of a present today is rude.
Poetry is the first major literary genre. All types of poetry share specific characteristics. In fact, poetry is a form of text that follows a meter and rhythm with each lines and syllables. It is further subdivided into different genres such an epic poem, narrative, romantic, dramatic, and lyric.
A genre is a specific type of music, film, or writing. Your favorite literary genre might be science fiction, and your favorite film genre might be horror flicks about cheerleaders. Go figure. In music, genre refers to musical style such as jazz, salsa or rock. In film or literature, the genre is determined by the subject, setting or plot of the story. When you are wandering around a book store, books are usually arranged by genre.