As an author, it is my job to paint pictures in my reader's minds using words. If I perform my job well, my reader will be able to form a picture in their mind of the characters, scenes and situations that I describe with my choice of words.
The most memorable books for me are the ones that lead me out of the real world and into other worlds where I could "see" and "hear" the characters and clearly picture their surroundings; I felt I was inside the story that the author had written; the story pulled me in and didn't let go until I finished the very last page.
If done well, written words can create a mood, evoke emotions and help paint a clear picture in a reader's mind of a scene or of characters. If written poorly, an author may only confuse and frustrate a reader as they attempt to understand the meaning behind the author's words.
Some authors go to extremes when trying to describe something in their story, using words which are overly descriptive or unnecessarily complex when simpler, clearer words could be used. I personally find such over-complicated writing off-putting and prefer a more concise description when reading a story.
My own descriptive writing tends to use easy to understand words, but that doesn't mean less effective descriptions. One of the greatest compliments I have received as an author is when a reader tells me that I painted such a vivid description of a place, character or event that they could picture it as clearly as if they were watching the story unfold in a movie. To me, that is praise at the highest level.
However you choose to use descriptive writing in your stories, keep in mind the feeling or mood you are trying to impart to your readers. Don't skip over the details of the scene that is taking place, but also don't go into so much detail that you bore your reader.
As an author, I act as a tour guide for my readers. I am taking my readers on a journey to new worlds, introducing them to new people and places. If I have done my job well, I will have entertained them as a reward for their investment of the time they have taken to read my book.