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.
Pastoral poetry is a genre that typically relates to country/rural life and often depicts the lives of shepherds. This sort of poetry describes the simple and pure lives of the shepherds, along with the notion that they are free from the corruption of life in the city.