is so called because every citizen
is able to voice their opinions and vote
on an issue. The result is what is often thought of as true democracy
(power from the people) since there is no elite
group that is in control such as in Representative Democracy
where a body is voted in to power to lead the state
for a period of time.
Direct Democracy is believed to originate from ancient Athens during the fifth century where Direct Democracy was used after a revolution against the King (their version of democracy is often referred to as Athenian Democracy or The Athenian Model). The population of Athens was 250,000 approx. but this includes women, children and slaves. In Athens at this time only adult men counted as citizens and so were the only ones allowed to take part. It is thought that there were about 40,000 citizens at the height of this democracy (around 490 B.C. after the Battle of Marathon).
Because of the relatively small size of the Athenian electorate it was possible to get them all together in an assembly and then to have a debate/vote. Nowadays with populations running into millions the electorate is too large to have such an assembly. Instead Representative Democracy is used. People get across their views in newspapers, books, television shows, films, articles, essays, dissertations, the Internet etc.. There are less options to replace Direct Democracy's ability to vote on issues directly. Referendums are as close to Direct Democracy as society can get with such large electorates.
N.B. People have played around with internet related direct democracy where you vote on an issue directly via a website. Obviously they failed but the thought was there. This is sometimes refered to as E-Thenian Democracy after the Athenian model described above.