Robert Sternberg's triangular theory of love categorizations love relationships into three components: passion, intimacy, and commitment. When arranged in a triangle, we get a conceptualization of the different kinds of relationships in life.
The Triangular Theory Perspective. This website is called Psychology Today and touches base on the different reasons people become attracted to each other and do get married or stay in a long, commited relationship.
Infographic explaing Robert Sternberg's Triangular Theory of Love