Tags are used to categorize your post. For example the tags you have used in this post are steemit, cryptocurrency, nigeria, stach, life. Meaning this post can be found in those categories when looking for other blogs/videos. It is best to use tags that relate to your post. Another example would be my blog: I post daily on cryptocurrencies so the tags i use are " cryptocurrencies, bitcoin, blockchain, money, news" because the content I provide is technical analysis on coins along with news. Hope this helps :)