system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does a "Board of Directors" work?

How are board members of large corporations also leaders of other companies? If they have such important jobs how do they find time to also be board members of another company? What about conflicts of interest? How do they become board members? Are they invited or do they apply? Are they paid a lot? Why do they appear to be relatively secretive (you can find board member bios but you have to dig for them and it's not common knowledge who they are). What is their role?
gpt
Board members don't have to be employees of the company and do its day to day decision making, like a CEO.

They can be independent business figures appointed by shareholders to have a say in the strategic direction of the company. They sign certain documents for the company, call meetings of shareholders, and give directions to the CEO on what projects to pursue.

Because they don't meet every day, but only every so often, they have time to do other jobs, like practice law or accounting, or to be on other company boards.

However, if a board member has a conflict of interest due to their role on another company board or whatever, they can't vote on that issue and may have to excuse themselves from the board roon when those meetings or votes are held.

Board members are often paid well by big companies, and usually have substantial shareholding in the company. 

They're not that secretive - all companies need to list their directors on a record with the body where they incorporated, so the public can look them up. This is important because directors can act to bind the company, so if you're signing a contract with another company you need to be sure that the person who's signing for that company is actually a director.