How do you explain the amphoteric behaviour of amino acids ?

Explanation

Amino acids are the compounds having amino group `(-NH_2)` i.e., a basic group and carboxyl group (-COOH) i.e., an acetic group
Zwitter ion : In aqueous solution of amino acids, the carboxyl group can lose a proton an amino acid can accept that proton to from a dipolar ion. This is called as zwitter ion.

In zwitter ion from amino acids behave both acidic as well as basic nature, therefore amino acids are amphoteric in nature.