AirBNB was great when it first started out. It was basically people renting out a room in their home for a night or two, for far cheaper costs than hotels and in areas where a hotel wasn't as readily available. It was a good way for those folks to make some cash on the side and helped the traveler find convenient low cost housing for a couple nights
Unfortunately companies and people decided they could buy up properties and start a business selling out rooms, prices skyrocketed and it no longer became worth it. I just stick to hotels now (or hostels if I ever decide to backpack through Europe or something)