please explain markonikov and anti markonikov rule.

In the presence of peroxide , addition of  HBr to unsymmetrical alkenes proceeds through radical chain mechanism.

Markonikov's rule states that the negative part of the addundum gets attached to the C having less number of H

Here you get 2⁰ Haloalkanes but in presence of peroxide you get 1⁰ bromoalkanes.