Evangelism refers to the practice of relaying information about a particular set of beliefs to others who do not hold those beliefs. The term is often used in reference to Christianity

Christianity

Christianity is a monotheistic religion based on the life and teachings of Jesus as presented in canonical gospels and other New Testament writings...

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Christians who specialize in evangelism are known as evangelists whether they are in their home communities or living as missionaries in the field.
Some Christian traditions consider evangelists to be in a leadership position; they may be found preaching to large meetings or in governance roles.
Christian groups who actively encourage evangelism are sometimes known as evangelistic or evangelist.