I've never been able to figure out what people mean by "tags" and what the benefits are, perhaps someone can enlighten me? I feel like the only problem with st

I've never been able to figure out what people mean by "tags" and what the benefits are, perhaps someone can enlighten me? I feel like the only problem with standard hierarchical file systems is that sometimes you want files to show up in multiple places. I think this is only a subset of files, typically "media." A photograph or a song often has multiple categorizations. However, a lot of things, like my tax documents, source code, Word documents, and notes typically only have one place they need to go to. It seems like symlinks or hard links are an already-existing solution; other than lack of great options on managing them, how do tags improve this? As far as I can tell, tagsistant does have hierarchical tags, so it isn't doing away with hierarchy, which is good. One problem with some tag systems (like Gmail's original) is that under "notes" I have "lectures," "stuff I want to remember," "things like list of books I want to read," "temporary." If I'm looking for photos, I really don't want to see a bunch of notes tags.