The main stakeholders are those who stand to be the most affected, either positively or negatively, by changes in a company. For instance, if a company is about to go bankrupt, the owners and employees are all main stakeholders because they will all lose their income as a direct result of the loss of the company.
When there are big decisions being made or big changes in a company, many different people are affected in different ways. Some are directly affected while others are indirectly affected later. The people who have a relationship with a company and stand to be the most affected by changes in that company are called primary or main stakeholders.