A board of directors has fiduciary responsibility to the shareholders of a corporation. As such they can hire and fire management (the CEO). If you form a corporation, the state will probably require a board, but in most states, you can be the sole shareholder, the entire board of directors and the CEO.
Angel and VC investors will typically require a seat on a board and that the composition of the board not be totally made up of founders. (Similar structure can be created for an LLC but the names are different.) But if your company is self-funded, then you may not want or need that.
You may want an advisory board. This has no legal or fiduciary responsibility but is composed of people you want advise from. This can range from an informal relationship to a formal structure with regular meetings. There are many ways to do it - beyond the scope of this forum.
Compensation ranges from "I'll buy the beer and be eternally grateful" to a small amount of stock (half a percent or maybe a bit more) to actual cash if the company is profitable.
I strongly suggest if you make any kind of formal board, that you limit the term of service to one year and say so at the start. That makes it easy to get rid of someone who isn't working out, and of course, you can always renew the term for someone who is.
And advisory board has no agenda other than what you give it (unlike a board of directors) so you have to do a bit of planning and prep to get the benefit. But when you do, it can be a wonderful thing.
Expertise on the board can be related to your market, your technology, your business organizational structure or whatever you need. Often a strong benefit to the board members is the ability to work with each other.