Modernism describes things you do that are contemporary or current. Your modernism may be seen in your up-to-date clothing, your contemporary taste in books, and your willingness to stay up on current trends.
Modernism can describe thought, behavior, or values that reflect current times, but it can also be used to describe an art and literature movement of the 19th and 20th centuries that intentionally split from earlier conservative traditions. The poet Ezra Pound was a key figure in modernism, and his famous slogan "Make it new!" sums up the values of modernism, which rejected traditional forms and styles for more experimental techniques.