Reactivity and the difference between the nucleophiles and electrophiles should be identified.
Electrophile (negative-charge loving):A molecule or ion that accepts a pair of electrons to make a new covalent bond is called an electrophile.
Electrophiles are neutral or positively charged species, having vacant orbitals and attracted electron towards itself.
Nucleophiles (positive-charge loving): A nucleophile is a more reactant species that affords a pair of electrons to the electrophile or electrophilic center and forms a new covalent bond.
The carbon or other hetero atom in a molecule which is bearing negative charge or lone pair of electron is called as nucleophiles.