The difference between friendship and companionship lies in the relationship intimacy. The relationship that companionship creates is universal, on the other hand, the relationship that friendship generates is particular.
Fellowship is the value of being a good person by helping people you know no need to interleave a link more intimate, on the other hand, friendship is a broader term than companionship, since it implies a long term built relationship.
Both friendship and companionship are based on values of solidarity, empathy, respect and tolerance.
Fellowship arises, for example, in moments of crisis where people have to support each other and work as a team. Whether at work or outside of it, companionship helps others without expecting anything in return and without needing to know the people.
The key to friendship is the knowledge of the other. Friendship is a bond of unconditional love where companionship arises from the feeling of helping who we love. Friendship demands loyalty, sincerity, commitment and reciprocity.
Those who are in a friendly relationship are called friends, which derives from the Latin meaning to love. In this sense, friendship is for friends and companionship for acquaintances.
When fellowship and friendship come together in a group with some kind of organization and constancy, they are called fraternity.