All that really matters to me is where they put them in the record shops that I tend to visit, so that I can find what I want, or similar stuff. This can vary shop by shop though - but usually not too much.
If in doubt just ask the shopkeeper.

If the shop didn't have enough stuff to warrant a subdivision, then the term doesn't matter. If you've started using more specialist shops, then it may start to matter.

If you're trying to understand music 'journalism' / marketing/PR bullshit instead of listen to music then I have no advice. I'd rather spend more time listening to some music/radio or just randomly going to concerts than reading 90% of the shite that people write about music.

The only real issue comes for very new groups where they don't even have a bandcamp to listen to or any half decently recorded youtubes. In those cases I'd expect ticket price to be just a few quid, so just risk it and go to the show. You can always leave if it's unbearably shite.

If you want to get an idea about a genre , try to pick up a cheap compilation or samplers, or find a radio show that might play it.