Tags are unstructured keywords, which refer to pieces of information, such as browser bookmarks, digital images, and files. Such metadata is designed to describe these pieces of information and help them to be found during the viewing process or through a search query.
It depends on the system, but in general, tags are used without hard rules by the person creating or browsing the data.
Tagging has become popular thanks to the Web 2.0 sites and services. Now it has also become part of some computer programs.
Tagging was created as a tool to aid in the processes of classification, identification, the indication of boundaries, and the definition of identity. It can be a word, an image or any other mark.
Just as in a museum we have referencing, help desks, and maps to guide us, so in the IT realm we have tags that carry us through the virtual web. They improve search queries, which in turn significantly make it easier to research information.
In earlier versions of sites, the tags were used by designers to inform the search engines about the content of the pages. Today meta tags are used for these purposes.
Websites that use tags often show a selection of popular tags in tag clouds. Custom tags are equally useful for both users and other site visitors.
Hashtag is a type of metadata, the record of which begins with a # (hash). This type of tag is common in microblogging and social networks - Twitter, Facebook, Google+, and Instagram.
It has its flaws, however, when it comes to spam. Information is often littered with redundant and superfluous tags.
In the hope of attracting visitors (for example, as in YouTube), people mark information with excessive tags that have nothing in common with the subject of information. In an attempts to overcome this problem, human verification and other statistical methods have been introduced to combat spam posts.
A further solution can be to simply limit the number of tags in a given object.