Brotherhood may be referred to as the feeling of oneness, among brothers or towards fellow human beings. It is also seen as a collective word for a group of people standing up for a common cause.
In common social parlance, when one refers to the feeling of brotherhood, it means the existence of feelings of togetherness and bonding.
As an organisation, a brotherhood refers to people coming together to work on a common objective, a fraternity. This can be a socially progressive objective like control of social evils, for mass education. But at times brotherhoods have also come into existence for anti-social causes e.g. for human slavery.
Mostly in past centuries, secret organisations like Free-Masons, used to come into existence united by a common purpose. The organisations used to refer to themselves as a brotherhood, that is people joint together in a feeling of brotherly love. This was generally to give the organisation a family-like feeling of bonding, and to the members a sense of intimate belongingness.
In today’s world, a Brotherhood can also be a group of anti-social elements focused on organised crime.