The importance of an imagery in a text is the imagery's ability to appeal to the senses of the reader. Many times, the descriptive nature of the piece appeals to multiple senses of the reader.
In Esmeralda Santiago's essay "How To Eat a Guava" (from her novel When I Was Puerto Rican), appeals are made to all five of the senses. It is her use of vivid imagery which allows this to happen.
The guave is not quite ripe; the skin is still a dark green.
It was large and juicy, almost red in the center, and so fragrant that I didn’t want to eat it because I would lose the smell.
Here, Santiago describes how the guava looks. Her word choice provides a very specific image for the reader: large, juicy, red.
When you bite into a ripe guava, your teeth must grip the bumpy surface and sink into the thick edible skin without hitting the center.
While not specifically appealing to the ear, one can (if engaged and experiencing the reading) hear Santiago's teeth sink into the guava. The sound of her teeth sinking into the flesh and grinding against the bumps of the skin echos in one's ears.
When you bite into a ripe guava, your teeth must grip the bumpy surface and sink into the thick edible skin without hitting the center. It takes experience to do this, as it’s quite tricky to determine how far beyond the skin the seeds begin.
You bite into it at its widest point, because it’s easier to grasp with your teeth. You hear the skin, meat, and seeds crunching inside your head, while the inside of your mouth explodes in little spurts of sour.
In Santiago's description of the taste of a guava, one can quickly recall similar instances where they, themselves, bit into something sour.
I pick one the size of a tennis ball and finger the prickly stem end. It feels familiarly bumpy and firm.
The reader can not only see the fruit, they can recognize the size of a guava by how a tennis ball fits in their hand. The rough surface is also described to provide more descriptiveness for the reader.
I smell it and imagine a pale pink center, the seeds tightly embedded in the flesh.
This can be the most confusing for a reader. For many, the smell of something "pink" is confusing. One would, most certainly, relate the smell to something else they have knowledge of being pink and fragrant.