Instead of providing plain information. propaganda mainly presents information selectively so that only the positive or negative parts of something are described; it may influence a group of people towards a cause either supporting it or opposing it.
Oftentimes leaflets were dropped on enemy lines to either notify citizens (possibly for safety) or decrease morale in enemy troops. Usually when propaganda is aimed at demoralizing enemy troops, the propaganda tries to demonstrate that surrender is better than to keep on fighting. There are also different types of propaganda, that use different techniques in order to affect certain group's attitudes.
One notable propaganda technique is called "Joining the Crowd," and it consists of persuading people to follow in the footsteps of the massses. This can be used to make more civilians enlist in the armed forces or to get more civilians to work harder in factories.
Modern propaganda was first notably implemented during Russian Revolution of 1917 and it was continually implemented throughout World War II. After World War I, one of the largest "propaganda machines" in the world became Nazi Germany through the spread of newsreels, newspapers, posters, magazines, public events, etc. The reichminister of propaganda for Germany was Joseph Goebbels. Still, during the war, almost every country produced large amounts of propaganda. This propaganda was used to attempt to get across multiple points ranging from the famous "loose lips sink ships" quote warning of the potential danger of letting loose information to general encouragment for civilians and soldiers alike.