Collaring represents the act of submitting oneself to the dominant. Often regarded as a powerful symbol in the world of BDSM, a collared individual publicly represents the D/s relationship between the two parties. Some people choose to have a formal collaring ceremony that is not unlike a traditional marriage ceremony. In fact, to most people who participate, a bondage collar is regarded as being synonymous to a wedding ring. It usually shows that the submissive in question is off-limit to other dominants.
In a more casual context, the act of being collared can also be used in light bondage or role playing.