Select any two works, one a comedy and one a tragedy. You can select modern stories or classic literature from Shakespeare. You'll find the basic structure of the genres has changed very little through the ages. Read each piece thoroughly, taking notes as you go. Your notes should address story, characters, plot turns and setting. Draw a vertical column on your notebook paper and make corresponding notes on these factors for both pieces you read.
Make a list in your notebook of contrasting elements in comedy and tragedy. This will help you better understand the differences between the two forms. Some examples. Character concerns in comedies are usually small in comparison to the world-changing concerns in tragedies. The hero in a tragedy may have a single flaw in comparison to the many flaws typical of characters in comedy. Tragedy often highlights the audience's limitations, while comedy often makes the audience feel superior.
Compare characters in comedy and tragedy. Characters in comedy are typically ordinary people thrust into extraordinary circumstances. Those circumstances result in challenges that lead to good fortune, whether monetarily, emotionally or both. This is in direct contrast to tragedy, where the main characters are heroes who are anything but ordinary. The hero in a tragedy almost always wins by sacrifice.
Compare settings in tragedy and comedy. Tragedies are set in absolute worlds, most often with hard lines drawn between good and evil. Comedies are typically real-world-based, and good and evil are either relative or irrelevant. Settings in a tragic world are often dark and dismal.
Note the endings of your two pieces. Tragedy ends unhappily, even when it can be considered happy for at least one character. The hero always makes a sacrifice to bring this about. Comedies have happy endings, often with the main character acting selfishly to achieve that happiness. This is often true of modern-day romantic comedy.