What do you mean by zwitter ion?

Explanation

Due to the presence of an acidic and a basic group in the same molecule, amino acids exist in an ionic form called a Zwitter ion where the proton of -COOH group is transferred to the -`NH_(2)` group.
`R-overset(NH_(2))overset(|)underset("Amino acid")(CH)-COOHrarrR-overset(+)overset(NH_(3))overset(|)underset("Zwitter ion")(CH)-COO^(-)`