The rules say that creatures in a heavily obscured area "effectively suffer from the blinded condition".

The blinded condition states that:

• attacks against a blinded target have advantage
• a blinded creature's attack rolls have disadvantage

So when the Darkness spell (just to use an example) is cast, combatants gain advantage and disadvantage when attacking others who are also inside the area.

Do I understand correctly that they then cancel each other, so attacks are made normally? If so what really changes?