A hostel is a form of low-cost, short-term shared sociable lodging where guests can rent a bed, usually a bunk bed in a dormitory, with shared use of a lounge and sometimes a kitchen. Rooms can be mixed or single-sex and have private or shared bathrooms. Private rooms may also be available, but the property must offer dormitories to be considered a hostel.  Hostels are popular forms of lodging for backpackers. They are part of the sharing economy.  Benefits of hostels include lower costs and opportunities to meet people from different places, find travel partners, and share travel ideas. Some hostels, such as in India or Hostelling International, cater to a niche market of travelers. For example, one hostel might feature in-house social gatherings such as movie nights or communal dinners, another might feature local tours, one might be known for its parties, and another might have a quieter place to relax in serenity, or be located on the beach.  Newer hostels focus on a more trendy design interior, some of which are on par with boutique hotels.  Some may cater to older digital nomads, global nomads, and perpetual travelers that prefer slightly more upmarket private rooms or a quieter atmosphere.

Many hostels are locally owned and operated, and are often cheaper for both the operator and occupants than hotels. Hostels may offer long-term lodging to guests for free or at a discount in exchange for work as a receptionist or in housekeeping.

There are approximately 10,000 hostels in Europe and approximately 300 hostels in the United States.  The typical guest is between 16 and 34 years old, although it can vary depending on the country.

In addition to shared kitchen facilities, some hostels have a restaurant and/or bar. Washing machines and clothes dryers are often provided for an additional fee. Hostels sometimes have entryways for storing gear. Most hostels offer lockers for safely storing valuables. Some bare-bones hostels do not provide linens.  Some hostels may have a curfew and daytime lockouts, and some, albeit few, require occupants to do chores apart from washing and drying after food preparation.

A mobile hostel is a temporary hostel that can take the form of a campsite, bus, van, or a short-term arrangement in a permanent building. They have been used at large festivals or trips where there is a shortage of lodging.

In some cities, hostels reported a higher average income per room than hotels. For example, in Honolulu, Hawaii, upscale hotels reported average daily room rates of $173 in 2006, while hostel rooms brought in as much as $200 per night, for rooms of eight guests paying $25 each.  Even during the financial crisis of 2007–2008, many hostels reported increased occupancy numbers at a time when hotel bookings were down.

A 2013 study in Australia showed that youth travel was the fastest-growing travel demographic and that the hostel industry was growing at a faster rate than the hotel industry. It showed that youth travel can lead to higher overall spending due to longer trips than traditional vacations.  In New Zealand, backpackers hostels had a 13.5% share of lodging guests/nights in 2007.