A lone pair electron is a pair of electrons that have not participated in bonding. This means they are not participating in any sharing phenomenon.
For example, when SODIUM is combined with CHLORINE to make NaCl, one electron out 7 valence valence electrons of chlorine gets combined with one of the valence electrons of sodium. However, there are still 6 valence electrons in Cl’s outermost shell and these are known as unshaired electrons.