Some of the most common questions asked by Cruise Critic readers involve cabanas -- what types are there, which ships have them, how much do they cost and what's included? We'll answer those questions below, but first, let's start with the basics:

What is a cabana?

The term "cabana" can mean lots of things. Generally, cabanas are small huts enclosed by walls or curtains for privacy, but since there are so many types, that's where the similarities end.

What is a private island cabana?

A private island cabana is a private, enclosed hut found on a cruise line-affiliated private island. Most are found on or near the beach, but some are located by a pool.

Amenities vary, but depending on the type, these cabanas might have an indoor lounge area with furniture and a television, air conditioning, a private bathroom, an outdoor deck with loungers and butler and/or waiter service. Private beach access might also come with your rental.

Cruise lines often list private island cabana rentals as shore excursions, meaning you'd book them as you would a tour. But be warned: They're limited in number and, therefore, often pricy. We've seen some cabanas go for as much as $600 for the day (for up to about eight people). And, if you wait until you're onboard to try to reserve one, you might be out of luck.

What is an onboard cabana?

An onboard cabana is a cabana found on the ship itself. They're usually located in private areas, such as adults-only enclaves or for-fee sun decks (like Norwegian's Vibe, a for-fee adults-only sun deck that offers cabanas for an additional per-day or cruiselong fee), and they often look a bit like open-air tents with loungers, a drinks table and curtains that can be drawn for privacy. Others are found in areas exclusive to passengers who book suites or cabins in certain ships' restricted-access areas, such as Norwegian's The Haven or MSC's Yacht Club.

Amenities might include complimentary snacks and the use of water misters and iPods preloaded with relaxing music.

Cabana access is often free on a first-come, first-served basis for passengers booked in restricted-access cabins or suites, or those who pay for entry to a fee-added sun deck.

Cabanas for which a full fee is charged are generally booked separately from shore excursions. Some lines allow online bookings before boarding, while others require passengers to book onboard. Demand is high, and space is limited, so prices are often not cheap. However, onboard cabanas often have fewer amenities than those on private islands, so the prices are usually more affordable. Plus the onboard variety can often be booked on a half-day basis, rather than full day, which drives the price down a bit more for those looking to save.

Lines offering for-fee cabanas include Norwegian, Seabourn, Holland America and Celebrity. Some lines allow cruisers to pre-book cabana rentals. Otherwise, passengers should visit the front desk as soon as possible on embarkation day or risk missing out.

What is a spa cabana?

Spa cabanas are found onboard some ships and ashore on certain private islands. These types of huts -- similar to the above-mentioned open-air tents with curtains for privacy and a massage table or two -- are used for massages and other spa services, offering an open-air experience.

There are generally no special amenities, apart from the spa service for which a passenger has paid.

Spa cabana services can be booked online ahead of sailing on some ships, or they can be arranged at the spa upon embarkation. Passengers do not get any additional use of the cabana beyond their treatment time; the cabana simply serves as the location for the alfresco massage. Standard massage prices generally hover between $100 and $250 per person, depending on the type and length.