"I wear a red coat."
きます is for clothes worn over the shoulders, like a coat, and はきます is for clothes that you step into, like pants (whichever meaning you use for that word...). To remember which is which, simply think of hakama (it doesn't actually use the same kanji, but it sounds like it could have).
It's an ending, making it (the positive non-past form of) an i-adjective. Without the い it is a noun ("the color red"), or part of a kanji compound. Unlike English, Japanese i-adjectives can be conjugated by exchanging the い for other endings, which is why it isn't included in the kanji.