What is the difference between Tag and Category?

Question

Search Engine Optimization

Consider the example of Steam , where in addition to tags for games, there are categories and genres.
What's the difference for example:
" Free " is a category, tag or genre?
Is " Shooter " a category, a tag, or a genre?
If we take OS, then it can also be TagEntity or PlatformEntity exclusively for these purposes.
How to find this edge?

Answer 1

Genre/Direction is always a fixed list.
1. The structure ("tree") of categories differs more often than the names of genres, categories and tags.
2. The sets of different tags and their total number are slightly different.
Hint: a good set of tags = a good recommender system

Answer 2

There are a limited number of categories. There are
an infinite number of tags.