The Board of Directors have a fiduciary responsibility to guard the interests of the shareholders of a company.
The board makes decisions on major strategic issues, and can often (but not always) fire the CEO.
In an early stage startup that has just raised a Series A, it's most common to have thee board members: two appointed by the founders, and one by the venture capitalist. Usually at each major subsequent round of funding, another board seat is created.
The SEC requires that the majority of the Board of Directors sign the Form C to fundraise on Wefunder.