What do you understand by the tag backyard-garden? It means nothing to me and I can't see what the 3/4 questions under that tag have in common.
But maybe it's a term in general use somewhere in the world, and means something?
As far as I know the tag is redundant with most people's use of gardening and should be edited out. Feel free to correct me if someone sees a need for this tag, but for now I would edit it out with prejudice, possibly going as far as to ask for it to be blacklisted it if it becomes a problem...
Well, your "front garden" faces the street, so it is much more likely to be ornamentals and managed for aesthetics.
Your "back garden" or "backyard garden" is hidden from street view. That's where you grow your potatoes, cabbage, etc.
I've heard that some HOAs/zoning ban vegetable gardens in the front garden. In those communities, corn or pumpkins in the front yard are illegal...
I think that's the rationale behind having backyard-gardening, but I agree that it's probably a useless tag. As wax eagle said, it's either redundant to gardening (which is redundant to being on this site), or it's redundant to vegetable-gardening.
+1 on getting rid of it.