Why is the buffer solution used in EDTA titration?

Hint: We have to know that titration is the way toward adding one solution (known molarity) to another solution (known volume; unknown molarity) until the reaction arrives at the equality point. The equivalent point is obtained by utilizing an indicator that shows change in color. Complexometric titrations are helpful for the assurance of various metal ions in a mixture. EDTA titration is a type of complexometric titration.

Complete answer:
We also need to remember that EDTA, ethylenediaminetetraacetic acid, has four carboxyl gatherings and two amine bunches that can go about as electron pair contributors, or Lewis bases. The capacity of EDTA to possibly give its six lone sets of electrons for the development of facilitated covalent bonds to metal cations makes EDTA a hexadentate ligand. Nonetheless, practically speaking EDTA is generally just mostly ionized, and along these lines structures less than six coordinated covalent bonds with metal cations.
EDTA frames an octahedral complex with most $ + 2$ metal cations, ${M^{2 + }}$ in aqueous solution. The principal reason that EDTA is utilized so broadly in the normalization of metal cation solution is that the development steady for most metal cation-EDTA complexes is high.
We have to know that the reason why the buffer is used in EDTA titration is because it avoids the pH change. This is due to reactions that are taking place between metal ions and EDTA. Both metal ions and EDTA are pH-dependent.

Note:
 In simple words, we have to remember that when a buffer is added to a solution that undergoes titration in desired range of pH because the binding sites on EDTA could stay active and is able to chelate ions of metal found in the analyte solution.