The simple meaning of economies of scale is doing things more efficiently with increasing size.
In an economic context, a scalable business model implies that a company can increase sales given increased resources.
What is scalability?
Scalability is a characteristic of an organization, system, model, or function that describes its capability to cope and perform well under an increased or expanding workload or scope. A system that scales well will be able to maintain or even increase its level of performance or efficiency even as it is tested by larger and larger operational demands.