Mountain climbing can be done under many different conditions, and as such, there are a lot of different forms of mountain climbing shelves. Seeing as different locations can have wildly different terrain and weather conditions, the choices available to mountain climbers vary based on location and the general expected needs of the climbers. These shelters are particularly important on longer climbs, when people spend days on the mountain to climb to the highest peaks.
Huts are extremely common forms of Shelters found in many European climbing spots. They can be found at different points along the mountains, and offer the basic necessities, such as a dining area and a place to sleep, as well as provide shelter should a climber need to rest, or unload some of their pack along the way. Huts vary in what they provide; some have staff year-round, some have seasonal staff, and some have no staff at all. Some of the more upscale staffed huts have diverse offerings that climbers can take advantage of, with food and drink made available. Others require the people staying in the huts to bring their own provisions. It is also important, when considering huts, to find out what they offer and if they are booked, as many cost money and accept reservations. This is particularly true of the huts with full-time staff.
Tents are also a very common choice for mountain climbing shelves. A climber simply brings a tent on the climb and secures it appropriatively. It is important to buy a tent that is strong enough to hold up to all weather, as many mountain climbers encounter snow, ice, and high winds. As such, using a tent is not always the safest way to go, especially if winds happen to collapse the tent or destabilize it in any way.
Some mountain climbers like to use snow caves as a basic form of shelter. They're warmer than tents, despite being made of snow, but in order to build a snow cave, a climber needs to have access to basic tools, the most important being a snow shovel. It is not that hard to build a snow cave; they can be built anywhere there is at least four feet of snow, which is a common condition for many mountain climbers to be in. A snow cave is not the same as an igloo, as it is far more simplistic and easier to build. Igloos are extremely uncommon shelters, as they are difficult to assemble.
Many climbers choose to rough it and go the route of a bivouac or a "bivy." A climber uses a Bivouac sack and a sleeping bag and rests, usually using a crevice or a trench as a means for shelter. Although some purists enjoy doing it this way, many climbers will consider this an option only in case of an emergency.
It is important to remember that mountain climbing is a very dangerous activity. One of the best ways to ensure safety is to be certain the proper shelter will be available, but also to have a back-up plan as well. If you are expecting to stay at a hut, for example, it is not a bad idea to have a tent or a bivouac with you, just in case something happens and you need to stop before you reach the hut destination. With potential changes in the weather, and the knowledge that anything can happen once you're on the mountain, this is some of the best advice someone can give you.