Ok, let me try to explain this..
For single wielding, as you level, your base attack bonus increases. You'll notice that once you get to a certain point, your base attack bonus gets to +6/+1. Thats when you go from having one attack a round with your PRIMARY weapon, to two attacks per round, both with your PRIMARY weapon (the first being at a base +6 to hit, and the second being at a base +1 to hit. So at +11/+6/+1 you'd get 3 attacks.
Duel Wielding grants ONE bonus swing with your OFFHAND weapon regardless of how high your base attack is or how many attacks you get with your PRIMARY weapon. So with a base attack bonus of +6/+1 a full round of attacks would be...
Primary Weapon
Off Hand Weapon
Primary Weapon
And at +11/+6/+1 it would be....
Primary Weapon
Off Hand Weapon
Primary Weapon
Primary Weapon
As for how you can get all your attacks.....
Move Action/Standard Action (single attack is a standard action) = You can move a distance greater than 5 feet and make ONE attack.
Free Action (5 foot step) / Full Round Action (taking all of your attacks) = You can move a distance less than 5 feet and make ALL your attacks (for most at lower levels this is still only one attack unless you are duel wielding)
Along with these actions you have to decide if you are going to fight defensivly BEFORE you start any of your attacks EVERY ROUND. Defensive fighting lasts only one round.
Let me know if you have any questions because i know this can be confusing and i'd like to have you get a good base understanding now.
And if i missed something Purity (or got it wrong somehow) please let me know, i'm one handed typing with a teething baby on my lap
