Hosts specify how many days and how many guests can stay along with a short comment with other restrictions or interests (no smokers, bring a tent, young people especially welcome, etc). The hosts enjoy having people from various countries stay at their homes while the guests enjoy free housing in the locations listed (although hosts may ask for reimbursement of incurred expenses). Also, guests may feel more at ease because many hosts are willing to assist with transportation and local information etc, and some also provide meals, although the only actual commitment on hosts is to offer overnight accommodation.
The Pasporta Servo is published every year by TEJO, the World Organization for Young Esperantists. Although the concept of offering hospitality to the traveler dates back to early cultures (notably ancient Greece), the idea of applying it specifically to Esperanto speakers began in 1966 in Argentina when Ruben Felman-Gonzalez started the "Programo Pasporto." Pasporta Servo in its current form was first published in 1974 with 40 hosts, under the guidance of Jeanne-Marie Cash in France. Both are still hosts in the Pasporta Servo.
The Pasporta Servo has enjoyed much use in the Esperanto movement as a means for promoting Esperanto, and is one reason why people start learning Esperanto. The official web site currently (June 2003) states that "It is even possible to recruit by means of the Pasporta Servo. Many people learn Esperanto only because they want to travel by means of the Pasporta Servo". (The word approximately translated here as "recruit" is varbi, a term also applied to military recruitment or religious conversion.)
See also: Hospitality Club