Attachment theory is a concept in developmental psychology that concerns the importance of "attachment" in regards to personal development. Specifically, it makes the claim that the ability for an individual to form an emotional and physical "attachment" to another person gives a sense of stability and security necessary to take risks, branch out, and grow and develop as a personality. Naturally, attachment theory is a broad idea with many expressions, and the best understanding of it can be had by looking at several of those expressions in turn.