Sure, sketches help us all visualize the same concept, but your concept should first be understandable, without any imagery at all. Just words.
Start by defining your product concept with a name and description.
The description should briefly summarize what your big idea is and what key benefit it offers your consumer.
The name should sum up the same in just a couple of words.
With just the name and description, you can already begin communicating your product concept to both yourself and your internal team.