Okay, let's say a weapon does 10 icons. Each one of those icons is going to do a specific amount of damage to your opponent, and that amount depends on your strength boost. The damage you do to an an opponent is the number of icons x your strength boost's damage multiplier (see the list at the bottom of this post).
So, your strength boost is the 85 boost (because 106 falls between 85 and 125), and your damage multiplier is 2.5. Let's say you use two 10-iconers. You'd multiply 20 (icons) by 2.5 (damage multiplier), and that 50 damage is what you could do using just those weapons.
Now let's say you train up to the 125 boost and use the exact same two 10-iconers. Your damage multiplier is now 3, so if you multiply that by the 20 icons, you would do 60 damage with the weapons.
The boosts happen at set points, so a pet with 125 strength will do more damage than a pet with 124 strength. A pet with 86 strength and a pet with 124 strength will actually do the exact same amount of damage, because both those numbers fall in the 85 boost.
But of course it's not as simple as that. That's just what's known as "base damage." When you pick an attack from the drop-down box (a "stance"), you can increase or decrease the damage. Selecting "berserk" will increase the damage you do by 50% but will also increase the damage done to you by 50%. Selecting "defend" will
decrease the damage done to you by 20% but will also decrease the damage you do by 20%. And of course if an opponent uses shields or something and blocks some of your icons, you will do less damage to them.
Defence is similar, but there are a couple different kinds of defence and it's complicated -- I don't think I can explain it well. But basically, having strength and defense in the same boost is preferred, and having a higher defense boost than your opponent's strength boost is always nice.
Strength and Defence Boosts/Damage Multiplier:
0 - 0.5
8 - 0.75
13 - 1.0
20 - 1.25
35 - 1.5
55 - 2.0
85 - 2.5
125 - 3.0
200 - 4.5
250 - 5.5
300 - 6.5
350 - 7.5
400 - 8.5
450 - 9.75
500 - 11.0
550 - 12.0
600 - 13.0
650 - 14.0
700 - 15.0
Read this for another explanation with some examples.
Also, play around with the
IDB Damage Calculator to see what your max damage would be at different boosts.