Informal helping is instrumental assistance, emotional support, companionship, or advice or information given to friends, neighbors, and extended kin (Voydanoff).
Informal volunteering or helping is the private and unorganized helping of friends, neighbors, and kin living outside the household. (Voydanoff citing Wilson & Musick)

As defined by Voydanoff citing Wilson & Musick: Wilson, J., & Musick, M. (1997). Who cares? Toward an integrated theory of volunteer work.American Sociological Review, 62, 694-713.