Letting complete strangers into your home might not sound like a good idea to everyone.

[Read more: Airbnb’s top 10 most desired properties revealed]

Neither, on the flip side, is letting yourself into the home of a complete stranger.

But for the many millions of users of accommodation-sharing site Airbnb, the idea isn’t just good, it’s brilliant.

Since the company launched in 2009, it’s grown from helping 21,000 guests a year find a place to stay to helping six million a year go on holiday, and currently lists a staggering 800,000 properties in 34,000 cities across 90 different countries.

There are some potential pitfalls with Airbnb – one woman in the US was so irritated by her nightmare guests that she had to pay them to leave her own home - but if six million people trust it and use it, it’s clearly worth investigating.

Here’s what you need to know about Airbnb.

1. How does Airbnb work?

Airbnb is an online marketplace which lets people rent out their properties or spare rooms to guests. Airbnb takes 3% commission of every booking from hosts, and between 6% and 12% from guests.

There’s plenty of criteria to list for/search a property: from a shared room to an entire house, to having a swimming pool to having a washing machine. There are photos of the property, and the hosts/guests, with full map listing.

2. Why do people like it?

A combination of factors, but primarily financial ones. Guests get good value accommodation at a huge range of price points, from a few pounds a night to hundreds and often in prime locations where a normal hotel would cost infinitely more.

Hosts can cash in on spare space, perhaps if children have flown the nest and there’s a spare bedroom. In fact, according to economist Dr Margarethe Theseira, if an Airbnb host lists their property for seven days a month on average they would earn £5,600 per year, a boost to household income equivalent to a 15% pay rise for an average full-time employee.

3. What are the other benefits?

There is more than a financial impetus though: many guests like living like a local and getting restaurant recommendations from people really in-the-know, while many hosts just enjoy meeting new people and showing off their home.

[Read more: 8 private islands you can rent on Airbnb that are cheaper than you think]

4. Is it easy to book?

Yes, very. Once you’ve created a verified profile (which can be linked to social media), you can send a message to the host and either book instantly, or submit a request for later booking. Hosts must show calendars of availability - most are kept well up-to-date - and they will inform you of what they will provide like towels or hairdryers.

It’s not advised if you’re travelling through though - many people don’t take bookings for just one night.

5. Are there any hidden extras?

It’s not really ‘hidden’, but many hosts will add a charge for cleaning on top of their basic nightly fee. This is always made clear on booking.

[Read more: Looking for travel inspiration? 5 ways we’ll be holidaying in 2018]

6. How do you get into a property if there’s no reception?

Once you’ve booked, you and the host will generally arrange where and when to meet, convenient to the property and your arrival time. This could be at the property itself, or if it’s tricky to find, many people agree to meet at a more central location and go from there.

Some Airbnbs are professional services rather than being run by a personal host, so you may meet one of their employees rather than the owner directly.

7. Then what?

They’ll show you around the property, give you details of local amenities and travel, then discuss where to leave the key when you leave.

8. But can you trust the people?

Yes. Firstly, there’s the peer-review system, where hosts and guests can leave honest reviews for each other; comments can only be left after a reservation.

There’s also the Verified ID system which confirms people’s identities by matching them with social media and other offline documents like scanning photo ID (this system is currently only compulsory for last-minute bookings).[

[Read more: Fancy holidaying in a castle or palace? 7 regal Airbnb residences you can stay in]

9. Can you trust the descriptions?

There’s always the danger, as with anything online, that things are not quite as they seem when you see them in flesh – but that’s where the reviews come in; only book somewhere with good ones.

10. And what about the money?

As a guest, you pay in full as you book through a secure platform, and hosts will receive that money 24 hours after guests check in.

11. What about refunds?

There are five levels of cancellation policies depending on the individual host. Generally speaking, you won’t get a refund for cancelling a trip at short notice but you might if there are extenuating circumstances or if there is something wrong with the property that wasn’t made clear in the description.

12. And for the host?

Airbnb has a 24-hour customer hotline for both guests and hosts, and for the latter, they recently introduced an insurance policy for any loss due to theft or vandalism - in Britain and 28 other countries, hosts are protected by a £600,000 “host guarantee”, backed by Lloyd’s of London. Airbnb recommends that hosts also have additional, appropriate home insurance.

For more information on hosting or booking, visit Airbnb.