YouTube Tags
Today, YouTube is looking closely at your tags. YouTube Tags are keywords used to describe your video content and make your video recognized by YouTube search engines, and when you write very good tags about your video, your video category, topic, and more will be easily recognized by Google and YouTube search.
engines indicate that your labels are the keyword to your video.
Keep in mind that when you search for any content on YouTube, the videos you get under the search box usually come with written tags and other metadata that are related or similar to the words you entered in your search box.
YouTube users search for videos by typing a few keywords, then basically click on the first 1 to 5 videos from the search, so you'll need to type unique, short, and descriptive tags to place your video there.
YouTube allows you to write up to 500 characters on a single video tag, but you should avoid spammy behavior, ie keep your tags short and descriptive.
YouTube has made it clear on its Support page that excessive labeling is even against their policy. When you type YouTube tags, pay attention to how your visitor can find your video in the YouTube search box.