There are two main types of electronic-voting machines and they each work differently. Paper-based systems use electronic machines to tabulate results recorded on paper ballots. Direct Recording Electronic systems allow input directly into the machine using buttons or touch screens, similar to how ATMs work.
Both types of electronic-voting systems allow much faster tabulation than plain paper voting systems that must be counted by hand. Direct Recording Electronic, or DRE, systems allow faster tabulation than paper-based electronic systems, as voters enter information right into the machine's databank. DRE systems can also display ballots in various languages and setups without requiring different paper copies.
Electronic voting machines also come with concerns about security and voter fraud. DRE systems, which do not keep any paper records, do not allow manual vote checking in circumstances of computer error or potential vote manipulation. Paper-based tabulation systems allow for manual ballot checking for as long as election organizers store the paper ballots. However, stray marks and errors on paper ballots sometimes confuse tabulation systems.
Electronic-voting-system manufacturers claim that their voting systems are very hard to compromise, but many detractors continue to lament the ease with which programmers might be able to modify election results, especially on DRE systems that have no paper trail. Other commentators would like electronic-voting-system programming code opened for transparent examination by the public, but this is likely to further increase the risk of unauthorized modifications.