Because of the different electronegativity of bonding atoms in the molecule, the density distribution of electron clouds in the molecule is uneven, and this effect is transmitted along the molecular chain through electrostatic induction. This electronic effect of the interaction between atoms in a molecule is called induced effect, in which if an electron is attracted by an electron with strong electronegativity, it is said that if an electron is attracted by an electron with strong electronegativity, it is induced to push the electron, while the electron with strong electronegativity has been induced to suck the electron.

Electrophilicity and nucleophilicity are two common reactions to study the reaction mechanism in organic reactions. To put it bluntly, nucleophilicity means that multi-electron groups attack electron-deficient groups, which we call nucleophilicity, while electron-deficient groups attack multi-electron groups, which we call electrophilicity.