Definition
An operating model describes how an organisation actually delivers: who does what, how work flows between functions, which decisions are made where, what technology underpins it, and how performance is governed. Strategy says what the organisation intends; the operating model determines whether it can.
The hidden decision inside other decisions
When an ERP is replaced, operations are outsourced or two companies are merged, the headline decision carries a second, larger one: how the organisation will work afterwards. Choose a platform before settling the operating model and the vendor's reference architecture becomes your operating model, not because anyone chose it, but because reversing it later costs more than anyone will approve. The same applies to outsourcing: the contract fixes an operating model for five years, whether or not the organisation designed one deliberately.
How designs fail in practice
Target operating models drawn as organisation charts, which capture reporting lines and miss how work actually moves. Designs that describe a destination with no credible route from the current state, so the organisation lives indefinitely in an unplanned hybrid of old and new. And ambiguity of ownership: when the design leaves two functions each believing the other owns a decision, the gap surfaces as a customer-facing failure months after go-live.