Similar things are alike. If you and your best friend both like walking, mystery novels, and chocolate, and you both dislike jogging, science fiction, and Brussels sprouts, the two of you have similar tastes.
The Latin root for similar is similis, meaning "like." If two movies have similar plots, you might like one better because it has a better script or more interesting actors. If you're tired of being told how similar you are to your long-haired, friendly mother, you could cut your hair. Or start being rude. Remember that similar ends in "lar" even though it might not sound like it.