Example:When you post a video on youtibe, it will ask you to add some tags, entering certain phrases that has something to do with the video your posting will help those who are looking find it. Example If you enter sora/riku/ect on a youtube search, a bunch of kindgom hearts videos with be be display depending on which tags were placed on the video and if they matched the tags searched for.
Pretty simple if you think about it.
Step 1 > User 1 posts a kingdom hearts video. > Step 2 User adds Sora/Riku/Kairi tags Ect to the video >Step 3 User 2 on youtube enters in sora/riku/kairi on the search function on youtube >Step 4: User 2 finds user's 1's video because of the matching tags.
Understand?