Tagging is a way of making a post more popular by adding a series of different words in the description. They work as a magnet of potential viewers of the users content.
In order to tag efficiently, the user must know what will attract their readership. For instance, if it is a blog about dogs and cats then the user would use words such as Pets, Dogs, Cat, Canine, Feline.
When I am writing into this blog, I am given the option to add tags. This is to simply catch viewers like a fish. I would use words such as Tagging, Digital, Communications etc to do this.