Defensive vs offensive mode

So I'm here running offensive mode on

And can't headshot or lasoo and on top of that do way less damage to someone that is on defensive mode?

And he can just headshot me if he wanted to?

Consider let's say we both standing and he pulls a gun and I don't have my hat on let's say(I run never without one)

Can somebody explain a little in detail in thiere words what's the difference how to distinguish it and how do you deal with it?

I appreciate the input

I'm not hating or being mad I'm just a bit surprised but at the same time I dont think I completely grasp the differences and the use of the modes.(Why are they even exist?

Don't we have parley for players that try to play online like it's some glorious single player mode