I don't know how common the concept of "the bench" is in consulting, but for my current and last positions, each firm has had "a bench". As in baseball, those not actively playing are on the bench, then when a project opening comes up for filling, you are put into play.
You can be on the bench for a number of reasons, but mainly the bench ends up having the weaker individuals or greener resources. The members are coming up, learning, or just suck.
This is fine, but what confuses me always is the type of work given to the bench. It's usually the work I want. Like, "go figure this out" or "automate that". These are huge opportunities, some rabbit hole the company has that could be fantastic, they give it to someone who might not be ready for it. Sure it might fail too, but these little projects are always the wild success stories we live for in technology and I want to work on them.
Most other companies give this proper names like "the lab" and the strongest most experienced resources are on this type of work giving it the proper attention. Why it has been downgraded in my current and past firms, I will never understand.