The GM decides what obstacles, people, traps, monsters, etc. The GM's world is usually a medieval one, but with magic, dragons, wizards, elves, etc. Typical adventures could involve rescuing people, exploring dungeons, or searching for knowledge, treasure, and power. Game sessions usually last from two to ten hours and future sessions start where they last left off. The average players of RPG's are males in their teens to early thirties.
Players are usually of an above average intelligence, and are creative, analytical and tireless.
They claim the person believed they were really the character they had created. The main fact is that absolutely no evidence of harmful effects from these games has ever been found. And RPG's have been studied immensely. James Forest and Suzanne Abyeta studied criminal tendencies of people who played RPG's and found that fewer crimes were committed by gamers than the average for each age group. You can do anything your wildest imagination will permit.