(N/A) The hydrohalogenation of an alkene is an electrophilic addition reaction where a hydrogen halide ($HX$,where $X = Cl, Br, I$) adds across the double bond of an alkene to form an alkyl halide.
Markovnikov's rule,formulated in $1869$,states that when an unsymmetrical reagent adds to an unsymmetrical alkene,the negative part of the addendum (the nucleophilic part of the reagent) attaches itself to the carbon atom of the double bond that possesses the lesser number of hydrogen atoms.
Example: The reaction of propene $(CH_3-CH=CH_2)$ with $HBr$:
$CH_3-CH=CH_2 + HBr \rightarrow CH_3-CH(Br)-CH_3$ ($2$-Bromopropane,major product) and $CH_3-CH_2-CH_2Br$ ($1$-Bromopropane,minor product).
According to Markovnikov's rule,the $Br^-$ ion from $HBr$ attacks the central carbon atom (which has fewer hydrogen atoms),leading to the formation of $2$-Bromopropane as the major product.