An airliner means a device used to carry passengers on a commercial basis. They are most often operated by airlines that own or lease. They serve the regular lines or are chartered to transport groups starting to commercial airports.
The vast majority of online service aircraft are designed exclusively for these types of uses, but in the first half of the twentieth century they were often developed from military aircraft bomber-type or transportation. Many are also available in freighter to transport cargo or passengers-cargo combined version. Old appliances sold on the used market are often converted for freight transport. Some devices have been built for the transportation of persons (heads of state) are used as a business aircraft or know military applications (troop transport, refueling, etc.).
Video credit: NASA