selective service system

     The Selective Service System, an agency of the federal government of the United States, is still commonly called the draft. Being drafted into the army means serving in the army because the government tells you to, even if you don't want to. Our government doesn't currently draft young men into the army, but they still have to register with the Selective Service when they are eighteen years old. If a young man hasn't registered, and is under twenty-six, he may still register and avoid prosecution for evading the draft.
     Draft registration is required in case our country becomes involved in a  major war and needs a larger army than volunteers can provide. Every American male is required to register. In the event of an actual draft, the disabled or unfit would be exempt from conscription.
     
    

the catch-22

    People claim to have read Catch-22 without "getting" what the catch was. Joseph Heller explains it plainly--perhaps the people who missed the meaning thought that he was joking, or having his character joke for him. The main character in the novel wants to get out of the army, so he tries to pretend that he is insane. The army will discharge him ( let him go ) if it finds that he is crazy. The problem is, the army psychiatrists tell the character that it would be crazy to want to be in the army. So since he obviously wants to get out of the army, he must be perfectly okay, mentally. So you can't get out of the army by claiming to be crazy, because it's perfectly rational to want to get out of the army--you might get shot, after all.