Things that are subjective are open to interpretation. If you go see a movie about a jewel thief, the topic is not subjective. But whether it's a good movie or not is subjective.
Subjective things depend on your own ideas and opinions: there isn't any universal truth. Subjective is the opposite of objective, which refers to things that are more clear-cut. That Earth has one moon is objective — it's a fact. Whether the moon is pretty or not is subjective — not everyone will agree. Facts are objective, but opinions are subjective. What's the best song, band, movie, or TV show? These are all very subjective issues. There's no right answer.
adj taking place within the mind and modified by individual bias
particular to a given individual
emanating from a person's emotions and prejudices
(of e.g. evidence) not objective or easily verified