For example, in the past, if a photographer was tasked with shooting publicity photos for a rock band, she might pull tear sheets from magazines (Rolling Stone, etc). She might have scrapbooks she has collected over the years. Or, she might keep a library of books of her own to show clients. She would meet with the band and show them her ideas for the shoot.
Now, she has the world at her fingertips with the Internet. And Pinterest can help her show it to the band.
All she has to do is create a Pinterest board for that project and start pinning things to it. She can invite someone in the band, or the whole band - to join Pinterest where they can see her ideas, comment on them, discuss them, etc. She can even add them as collaborators on that board (or another) and get their own ideas.