Many people hear the word missionary and think of people going to foreign countries to convert people to Christianity. And while many missionaries do fit the above description, not all that use the title fit that bill. They might represent a different religion. They might serve in their own country. In the widest sense of the word, many other people are on "missions", that may or may not have anything to do with religion: salespeople, recruiters, news reporters, teachers, etc.
The missionaries I will most often speak about are those who represent the Church of Jesus Christ of Latter-day saints, commonly known as "Mormons". While there are some 55,000 people serving full-time LDS missions around the world, they are not all young men between the ages of 19 and 21. A growing number of young women serve missions, I believe which are usually shorter than those of their male counterparts. And numerous senior couples serve missions.
And while many of the missions are of a proselytizing nature, there are several dozen other types of mission opportunities listed on the Church's website at lds.org, covering a wealth of subjects from Accounting and Finance to Welfare and Humanitarian missions.
In fact, it can be argued that everyone belonging to a group is, essentially, a missionary for that group.
The first reference to "member missionaries" I can find in a cursory search at lds.org is to an article in the June 1989 Ensign magazine, titled (aptly enough), "Every Single Member a Missionary". I must admit my own faux pas here and say that I read this to mean that each and every member could be/was a missionary. After reading the article just now, the author was referring to unmarried members. But, with slight modifications, the suggestions can apply to any member.
So, my challenge today to myself (and anyone else who want to play), is to share your faith with someone whose views are unknown to you or different than yours. Please be respectful of those with other points of view. And people of any faith are invited to join in! Have a great week!