A Journey Ring is a symbolic piece of jewelry. It can symbolize many things, but all of the symbolisation relates to a relationship status of some kind. It is called a "Journey Ring" because it starts out small and gradually gets bigger in size, usually in a circular shape, which symbolizes the way a relationship grows and changes over the course of time, or over the course of a life's journey.
A Journey Ring is most commonly related to a marital relationship. A husband might buy a Journey ring for his wife to symbolize his growing affection for her. The ring will most likely be created using diamonds, to represent the value that the giver places in the receiver of the gift.
Another common purchaser of a Journey ring is a fiance. If a couple decides to stay engaged for a long period of time, a man might buy his fiance a Journey ring to symbolize the idea that his feelings for her are growing more and more, despite the fact that the wedding has not yet taken place.
Still another purpose of a Journey ring is to show commitment between a boyfriend and a girlfriend. A man might buy his girlfriend a Journey ring to show that he is committed to her and that he is no longer interested in dating casually, but wants to nurture his relationship with her and only her.
Confusion: Promise Rings
Journey rings should not be confused with Promise rings, which are also commitment rings but do not hold the gradually-larger diamonds. The main difference in Promise rings and Journey rings is that a Promise ring symbolizes a promise for the future or a promise for future engagement or marriage. A journey ring is not a promise but an expression of still changing (in a positive way, of course) and growing feelings.
The Journey ring should not be given lightly. It would be a highly inappropriate gift for, say, a first date, but it is a very popular and generous gift for the modern, committed couple.