求翻译：志愿者主要从所学专业为对外汉语、汉语言文学、外语、教育学、历史、哲学等文科专业的在职教师、在读研究生、本科以上应届毕业生中招募选拔，经培训合格后派出任教。志愿者任期一般为一年，任期届满履职考评结果良好以上者，如本人和接收机构提出续任要求，经国家汉办审批同意后可以续任。志愿者服务年限原则上不超过三年。是什么意思？

Volunteers, mainly from the profession as a foreign language, Chinese language and literature, foreign languages, education, history, philosophy and other liberal arts in-service teachers, graduate, undergraduate recruiting graduates in the selection, the training of qualified sent to teach. Volunte