The VVPAT, or Voter Verifiable Paper Audit Trail, is an EVM-connected verification printer device.
It allows voters to verify if their vote has indeed gone to the intended candidate by leaving a paper trail of the vote cast.
It is an adjunct machine connected to the ballot and control units of the EVM. After the voter casts his or her mandate by pressing a button in the EVM, the VVPAT connected to it prints a slip containing the poll symbol and the name of the candidate.
Slips from a randomly selected polling booth from each constituency are then matched with the EVM tallies during counting to check for the accuracy of the process.
The VVPATs were added to bring in accountability to the voting process, with many parties questioning whether the EVMs were indeed malpractice or rigging-proof.
EVMs, in use since 1998 in India, have been gradually upgraded with security features and the ECI has suggested that it has robust procedural and technical safeguards to prevent EVM-tampering and electoral malpractices such as rigging.
The VVPATs were introduced in the past year and were universally used in the Assembly elections in Goa in February 2017.
But the addition of the VVPAT has also increased the complexity of the otherwise simple single programmable chip-based device, rendering it more prone to glitches.