Merriam-Webster defines trope as a “figure of speech.” For creative writer types, tropes are more about conveying a concept to the audience without needing to spell out all the details.
The wiki is called “TV Tropes” because TV is where we started. Over the course of a few years, our scope has crept out to include other media. Tropes transcend television. They reflect life. Since a lot of art, especially the popular arts, does its best to reflect life, tropes are likely to show up everywhere.