While fat bikes can be ridden anywhere, they really shine when riding sand and snow. They can also provide really good traction on wet rocky trails as well. The downside to fatbikes, as stated above, is the increased rolling resistance. If you’re considering going fat I would recommend purchasing a bike with the capability of running “plus” tires. For my Beargrease, I have an extra set of wheels that I swap out (27.5fat vs 29plus). In fact, I run the bike with 29+ on single track since it’s way faster for me and I’ll only run 27.5F when there’s more than 2-3″ of snow.