Hello, My Writing Colleague,
By definition, a trope is a common theme or device. In regards to fiction writing, these are the familiar hoops that characters jump through. They differ somewhat depending upon the genre.
For example, common Sci-Fi tropes include interstellar travel, time travel, and superpowers.
Romance tropes include one lover has social status and money and the other doesn’t, an accidental pregnancy, and forbidden love.
YOUR ASSIGNMENT: Make a list of the tropes you are including in your work in progress.