I dunno. Vote and stuff I guess. 

 Try to avoid splinters or falling off (or both🫨🫨🫨) 

 It all depends on the organization. Sometimes the role is very active (organizing activities, people, funds, etc),. For other organizations, the board members may act more like subject matter experts, and only become active when something calls for their expertise. 

For most businesses, it is similar to a council of elders, making sure the larger picture has an optimal goal.