Appreciation means to recognize and/or enjoy the good qualities of someone or something. Poetry appreciation is that attitude about poetry.
Some people flat out enjoy reading poetry. There isn't a single reason why people that enjoy reading poetry enjoy poetry. It could be because they enjoy the rhythm that the poet establishes with the words. It could be that they enjoy the rhyme. It could be because they enjoy the vivid imagery that is created in a tighter form than prose offers. It depends on the poem, and it depends on the reader.
What I like most about the definition of appreciation is the word "recognize." You don't have to enjoy poetry in order to appreciate what poets are able to do with words. Take the Shakespearean sonnet for example. All of them are 14 lines long. All of them are written in ABABCDCDEFEFGG rhyme scheme. All of them are written in iambic pentameter. You might think that reading poetry is pointless and tedious, but you can't take away the fact that writing a poem that adheres to that rigid structure is amazing. You don't enjoy reading them, but you recognize and appreciate the skill that went into crafting it. That's poetry appreciation.