Conway's law is a statement that organisations design systems that mirror their own communication structure. The exact wording of Melvin Conway is:
Any organisation that designs a system (broadly defined) will produce a design whose structure is a copy of the organisation's communication structure.
The premises of the statement is that in order for a software module to function, multiple authors need to frequently communicate with each other. The present social boundaries in that communication ultimately lead to the system created.
There is a strong relation between the organisational design and the software architecture. The way the organisation is modeled basically is the initial design of the software architecture.