Mood boards can be a great way to start the design conversation with the client, focusing on their wants and finding common ground in a creative and open way, without being too prescriptive at the start.
This is a step that has been perhaps missed out of elearning in the past, but with age of the internet and the expanse of the design and marketing industries reaching into every area of our lives, great design is expected, and everyone wants to have their say on how it is done.
It is easy to get carried away in a design process leaving out the client till you have committed to something you love only to find they don't, and then everyone feels a bit let down.
The type of mood board need for the project can vary, but I think it is always a great place to start.
A picture is worth a thousand words, and mood boards are a great tool to create that picture for your client.