Conditional Statements in Macros

I had done some digging around, looking for a way to do some kind of IF statement. I want to do the following:
if(1d20)>@{target|AC} then **Damage**: [[3d6]]

I came across this, in a article claiming it was a workaround for an if-statement in a roll20 macro.

[[ 1d12 + 5[STR] + ( ?{Two-Handed Weapon?|0}[TwoHanded?] * floor( 5[STR] * .5) ) ]]

Can someone explain that bit of macro for me? I am an experienced coder, but don't have mentor-status, thus I am limited to macros, rather than using an API.

[[ 1d12 + 5[STR] + ( ?{Two-Handed Weapon?|0}[TwoHanded?] * floor( 5[STR] * .5) ) ]]

The intention, here, is that the user of this macro would input 1 into the Roll Query when the user wishes the macro to add 1.5 times their strength modifier to a roll. That is to say, ?{Two-Handed Weapon?} == 1 implies that
[[ 1d12 + 5[STR] + ( ?{Two-Handed Weapon?|0}[TwoHanded?] * floor( 5[STR] * .5) ) ]]
= [[ 1d12 + 5[STR] + ( 1 * floor( 5[STR] * .5) ) ]]
= [[ 1d12 + 5 [STR] + floor(2.5) ]] i.e. [[ 1d12 + floor(7.5) [STR * 1.5] ]]

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It's not possible to truely hide macro elements using conditional logic without the usage of the API, which is only available within games created by Pro users.

That said, while "if(1d20)>@{target|AC} then **Damage**: [[3d6]]" may not be achievable, you may be satisfied with "if(1d20)>@{target|AC} then **Damage**: [[3d6]] else **Damage**: [[0]]" using a binary technique similar to above (in conjunction with Target Number / Successes). e.g.

**Damage**: [[ {1d20 + ?{Modifiers|0}}>@{target|AC} * [[3d6]] ]]