How are electrophiles formed?
Electrophiles, are electron loving species. They are positively charged, so they are electron deficient.
They are formed due to differences in electronegativity.
Most common example occurs in halogenalkanes, where the halide bonded to the carbon is more electronegative than carbon. So it attracts the bonding pair of electrons to itself leaving the carbon with less electrons. It becomes an electrophile.
Electronegativity is the ability of a species to attract a bonded pair of electrons.