Translation:I wear a black skirt.
”I wear black skirts" can refer to habitual action, as in "I wear black skirts every day". Presumably it's only one skirt at a time, but the speaker has multiple black skirts that they wear. Using the singular would imply to me that the speaker only has the one black skirt that they wear on occasion (while if you wanted to describe what they have on at that very moment the progressive would be more natural, "I'm wearing a black skirt")
Using "a" and "the" are imcredibly important to English speakers. They are adjectives that specify what the noun is. If you say, "i wear a black coat" then it means that you could be wearing ANY black coat. However, if you say, "i am wearing the black coat" then it means that there is one, out of all of the black coats, that you wear specifically. It is a bit of a bad explanation however, because in that example it would be better to use, "i am wearing that black coat" which would mean you're talking about a coat across the room you are going to wear in the future continuum tense. If you say, "i am wearing this black coat" then that coat is with you, you may be already wearing it or not. Who knows. Back to the original question, if you only say, "i wear black coat" or "i am wearing black coat", we will still understand what you are trying to tell us, but it really important to learn eventually. Not to mention, not using them makes you sound not very fluent. Most english speakers are very forgiving about those learning our language and won't sweat it. Whereas, many english speakers dont overemphasize the importantance either because many languages simply dont have them the same way we do. Spanish does to an extent, but isnt as much. I hope this helps and i encourage you to keep learning:)
"kiru" is just the plain version of "kimasu", or the other way around, "kimasu" is the polite version of "kiru", they both mean to wear somthing on your upper body, like a shirt or jacket. "hakimasu", as well as its plain version "haku", mean to wear something below your waist, such as pants or shoes.
In English there is a big difference between "I'm wearing a skirt" and "I wear a skirt". There isn't in my mother tongue. In this example Duo accepts both answers. Does that mean there is no difference in Japanese or should the て＋います form be preferred when saying "I'm wearing sth" ?