As the term is most commonly used among Christians, a missionary is a person who travels to a different regions, often a foreign country, to perform charitable work and spread the good news of salvation through Jesus Christ.
Often a large church will directly sponsor a couple or family in their mission by providing financial assistance and praying for them. Lifeway Chapel supports many missionaries by contribution to a general missions fund through the Assemblies of God. You can read more about Assemblies of God missions here.