What is Direct Democracy? How does it compare to other forms

Wiki gives us a good start...

Politics (from Greek: Πολιτικά, politiká, 'affairs of the cities') is the set of activities that are associated with making decisions in groups, or other forms of power relations between individuals, such as the distribution of resources or status. (I like this bit - the Swiss even decide how much to tax themselves)

The branch of social science that studies politics and government is referred to as political science.

(hence how and why the 'political class' has emerged. This includes our representatives (selected by the Political Parties, not by us) and their supporting bureaucrats). 

And they seem to live in a world of their own - rarely seen, only at Election time.

See more of the Wiki Definition  here.