Yeah, here's an attempt to explain it:
By default, on the player's turn, you get 1 attack. An attack is an attempt to hit.
If it's successful (you roll the target number), that 1 attack does 1 hit.
The "Haste" effect gives you one more attack per turn.
Now you have 2 attacks. You roll for each attack separately, so each has a chance to be successful or not. If either of the attacks is successful, it does 1 hit.
The "Flurry" effect gives you +1 hit on a successful attack.
If you had both Haste and Flurry, you'd have 2 attacks. If one of the attacks was successful you'd hit 2 times. If both were successful you'd hit 4 times.
Does that make sense?