Proverbs is—like Ecclesiastes and, in a different way, Job—a work of ancient Near Eastern Wisdom literature. Unsurprisingly, this is probably best defined as literature dealing with wisdom—what it is and how to get it. The genre extends back to such super-ancient works as the Egyptian "Instructions of Amenemopet."
You probably already get the concept of wisdom pretty intuitively, but just in case you don't: wisdom, in ancient Israel, represented the accumulated knowledge of generations and generations of people who didn't want the next generation to make the same mistakes that they did.
In Proverbs, which is basically a collection of aphorisms, or pithy sayings, it ranges from simple agricultural advice to guidance on spiritual formation (see here for more on that). Each little saying represents a mini-rule, meant to help the reader live a good life, in accordance with the rules of the world (as the wizened elders surmised them).
Basically, Proverbs represents the passing down of core life truths, many of which still resonate today. Don't lie, try hard, speak carefully—good stuff, eh?
Proverbs exemplifies this wisdom tradition in its straightforward, classic, Israelite form, and later works from the Apocrypha like The Wisdom of Solomon and Ecclesiasticus carried on the tradition. You can easily see these as being some of the first self-help books—like the How to Win Friends and Influence People or Wherever You Go, There You Are of the ancient world.
P.S. We should note that Proverbs is the second book in the Hebrew Bible's Ketuvim, or "Writings," section, which also includes works like Job, Ecclesiastes, and Song of Solomon.