What is the significance of Election Photo Identity Cards (EPIC)?

Hint: The next step after the constituencies are decided is to decide who can and who cannot vote. The preparation of the list of those who are eligible to vote is done much before the election and is consequently given to everyone in a democratic election.

Complete answer:
We follow an area-based system of representation in our country. For purposes of elections, the country is divided into different areas which are called electoral constituencies. The voters elect one representative from their area. A special system of reserved constituencies was made by the makers of our Constitution for the weaker sections of the society. Such constituencies are reserved for people who belong to the Scheduled Tribes (ST) and Scheduled Castes (SC).
The list of those who are eligible to vote is commonly known as the Voter’s List and is officially called the Electoral Roll. All the citizens aged 18 years and above can vote in an election in our country. Regardless of caste, gender, or religion, every citizen has the right to vote. Some persons with an unsound mind and criminals can be denied the right to vote, but only in rare situations. The government is responsible to get the names of all the eligible voters put on the voter’s list. The names of those who move out of a place or those who are dead are deleted and names of the new persons attain voting age are added to the voters’ list. Every five years, a complete revision of the list takes place. This is done to make sure that it remains up to date. A new system of Election Photo Identity Card [EPIC] has been introduced in the last few years. The government has attempted to provide this card to every person on the voter's list. When the voters go out to vote, they are required to carry this card so that no one can vote for someone else.

Note: But the EPIC card is not compulsory for voting yet. The voters can show many other proofs of identity for voting like the ration card, driving license, aadhar card, PAN card, passport, passbook issued by bank or post office.