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.
GENRE: A type or category of literature or film marked by certain shared features or conventions. The three broadest categories of genre include poetry, drama, and fiction. These general genres are often subdivided into more specific genres and subgenres.