A preposition is found in a sentence in which it introduces information to the reader like a location perhaps. The object of the preposition can be a noun, a pronoun or even a gerund that is usually together with the preposition in order to complete a prepositional phrase. In the statement above, the prepositional phrase is "on the garden", therefore the preposition is "on" and the object of the preposition is the "garden" to which the preposition "on" refers to.
. She is an adult when telling the story and she is looking back on the memories of her childhood. She is telling the story in 3rd person and since she is older, has a more mature view of what she did when she was younger.
