AirBnB offers a range of more interesting places to stay than a predictable hotel room. Like a hotel, you pay per night (plus some extra fees). Anyone can list their place on AirBnB.
Where it loses against a hotel is that since there is usually no staff to meet and greet you, more communication with the owner of the place is necessary to make sure that you can actually find the place and get the key. This involves several messages back and forth between you and the host, detailing exactly when and how you are going to arrive. Usually hosts try to be helpful, often offering to pick you up at the train or bus station.
AirBnB tries to restrict off-site deals directly with the hosts, so that they don't lose out on the commission fee they would get. They do this by censoring certain words. Sometimes this system is a bit overzealous. If you try to tell your host "my train will arrive at 17:00", fearing those numbers are a telephone number, AirBnB will pass them to the host as "my train will arrive at <phone number censored>".
Where it gets a bit ridiculous is when I tried to tell the host "you can see my couchsurfing feedback here: http://www.couchsurfing.org/bemmu". This was sent by AirBnB as "you can see my <website censored>". Not only was the link censored, but the word "couchsurfing" itself was censored.
Why hide this mysterious "couchsurfing" thing? I wanted to balance the situation by telling you what it is, in case you have never heard of it.
CouchSurfing is another accommodation booking site, similar to AirBnB. The difference is that in CouchSurfing, no money exchanges hands. Instead it is based on friendliness and good will. I have an apartment in Japan. We have some space. You want to visit Japan. Not a problem if you want to crash here for a night. If we ever visit your country, maybe you will also let us sleep at your place. And while you happen to be here, let's also have some interesting conversation over dinner.
They are not a direct competitor. We use both. We host people, because it makes for a fun weekend activity. We get to learn about the world directly from people with various lifestyles and experiences we never had. Interesting and educational. But when we go out on holiday, we still use AirBnB or hotels, because booking is easier and we can better choose our own schedule.
Hotel: $100 and super convenient. AirBnB: $50 and semi-convenient + more interesting than a hotel. CouchSurfing: $0, not always convenient, but super interesting.
In other words, CouchSurfing is for making international friends. To the censors at AirBnB, this is apparently terrifying.