There are many strict rules when you create new Topics.
I am explaing the Use of tags here.
01. If you create a topic that is already there so your topic is been deleted. So in order to create a useful topic you should use search bar to see if the particular topic is already there or you can create yours. For this you will provide keywords and the match will be only possible if the old topic creator has put right tags.
02. You have to put right keywords/tags so that others can search it properly.
03. Tags should be unique and more than one for each topic.
04. Put only relevant tags.
Please let me know if I missed anything.