Electrophilic addition is a chemical reaction where an electrophile reacts with a nucleophile, typically involving unsaturated compounds like alkenes or alkynes. In this process, the double or triple bond of the unsaturated molecule breaks, allowing new atoms or groups to attach. This reaction is crucial in organic chemistry for forming more complex molecules. During electrophilic addition, the electrophile, which is electron-deficient, seeks out the electron-rich nucleophile. For example, when hydrogen bromide adds to ethylene, the double bond opens up, and bromine and hydrogen are added across the former double bond. This transformation is essential for synthesizing various organic compounds.