At the school we have just left, the Parents and Friends committee was primarily for fund raising and doing nice things for the kids.

So they would raise money for big and small projects
Run things like soup days, pies days, toastie days for the kids (no canteen to days like that were pretty important)
Organise school BBQ's for families
Manage the uniform exchange.

All this had to be approved by school council, so they could not just do what they wanted, but generally Council approved everything.

Ours struggled for members, smaller school, but two members were very painful to work with, one excruciatingly so, who sadly was is the President. Basically she was so up her self and rude to everyone, she genuinely believed she was right and felt sorry for anyone who could not see her way. There were parents eager to help, but refuse to work with her.