Duopoly is a form of oligopoly Market in which only two firms
dominate the whole market for certain goods and services. They may
either produce same or similar kinds of goods and services and
control the whole market.
A real world example of a duopoly is a Market of two dominant
technological companies Apple and Microsoft.
Apple and Microsoft companies have always been old competitors
and they dominate the whole technological Market.
A Cartel refers to a group of producers or firms that join the
group Inorder to take important decisions on the price level to be
set and various output decisions.
A well known and the most Important real world example of a
Cartel is IATC.
IATC or the international air transport corporation is a cartel
as various members sit together to make various pricing
decisions.