First of all, you only ever get 1 attack in a Full Attack, unless an ability says otherwise; as long as your natural BAB is equal to your level, you may take 10 on your attack rolls.
However, starting at 6th level, you gain the ability to make a second attack at your full attack bonus; all attacks in a Full Attack must be targeted at the same creature (representing the fact that you aren't striking out multiple times, but are instead you moving the weapon in such a way that it really messes up the creature's innards); the only exception to this is when you are two-weapon fighting (which is an automatic thing; you don't get extra attacks from Two Weapon Fighting, but in return there is no feat tax. More on that later.), and when you kill or destroy a creature, in which case you may strike a different soon-to-be corpse (no point in clubbing a dead horse over and over again, is there?)
At +6 BAB, this brings a -2 penalty on all attacks in this round; at +11 BAB, this penalty goes away, and at +16 BAB, you get a +2 to hit on all attacks this round, as the placement of your weapon better lets you aim where you strike and how you twist that dagger
just right to inflict maximum damage.
In addition, at +5 BAB, whenever you make a full attack, you get a +2 bonus to your AC for that round, as you correct your posture through an all out assault; this bonus to AC goes up by 2 at +10, +15, and +20 BAB. At +7 BAB, whenever you make a Full Attack, you may also make an attack as a Swift action; at +14 BAB, this is improved to making an attack as an Immediate action.
Finally, at +12 BAB you may double the damage each of your attacks does for that round whenever you make a full attack.
My Thoughts (Why I did this)
Because it lowers the average number of rolls in a round; and believe me, I like that. I like that immensely.
People are actually dealing much larger amounts of damage now (compare a +20/+15/+10/+5 full attack to a +22/+22 full attack that automatically doubles its damage, with the option to attack someone as an Immediate action, if you feel like it.)
Plus, that take 10 thing at the top lets you find your sweet spot... and lets you keep hitting it.