https://www.wsws.org/en/articles/2022/09/13/zkyk-s13.html
For some info about rank-and-file committees, they are orthogonal to unions (you can be in a union and a rank-and-file committee) and are structured as institutions of direct worker organization and action as a way to ensure that worker demands and voices are paramount and to protect against the possibility of union bureaucrats reaching a deal with the company behind closed doors and attempting to ram it through the union undemocratically. The interests of workers must always come first before the ruling class, corporations, and even paid union officials.
For much greater detail about rank-and-file committees, see:
https://www.wsws.org/en/articles/2022/08/17/irfc-a17.html