Those are iterative attacks.
You get to make an attack at each listed bonus when you make a full attack.
A level 1 monk can make 1 attack with a +0 bonus, or two attacks, each with a -1 bonus, if s/he decides to use Flurry of Blows.
A level 16 monk can make 3 attacks, one at +12, one at +7, and one at +2. Or, if s/he uses Flurry of Blows, make 7 attacks: two at +14, two at +9, two at +4, and one at -1.
Note that those are only the bonuses from base attack. Other bonuses, such as strength bonus, magic weapon bonus, etc. are applied to each attack.
From the Pathfinder Core Rulebook, p187:
A full-round action requires an entire round to complete. Thus, it can't be coupled with a standard action or a move action, though if it does not involve moving any distance, you can take a 5-foot step.
If you get more than one attack per round because your base attack bonus is high (see Base Attack Bonus in Chapter 3) ... you must use a full-round action to get your additional attacks.
If you get multiple attacks because your base attack bonus is high enough, you must make the attacks in order from highest to lowest. ...
It doesn't actually explain base attack bonus in chapter 3, of course. It's cunningly hidden in Chapter 1.
From the Pathfinder Core Rulebook, p11:
Base Attack Bonus (BAB): Each creature has a base attack bonus and it represents its skill in combat. As a character gains levels or Hit Dice, his base attack bonus improves. When a creature's base attack bonus reaches +6, +11, or +16, he receives an additional attack in combat when he takes a full-attack action.
It's not clearly explained here, but the additional attack is at a bonus equal to the bonus of your lowest extra attack minus 5.
From the Pathfinder Core Rulebook, p57:
Flurry of Blows(Ex): Starting at 1st level, a monk can make a flurry of blows as a full-attack action. When doing so he may make one additional attack ... For the purpose of these attacks, the monk's base attack bonus from his monk class levels is equal to his monk level.
Thus the monk has two choices for iterative attacks: he can make a normal full attack using his regular (lower) BAB, or he can make a Flurry of Blows full attacks, which gives him several additional attacks but restricts him to unarmed strikes and special monk weapons.