What's the difference between the Actor Model of Concurrency and Communicating Sequential Processes I'm trying to wrap my head around what the real differences between the Actor Model of concurrency and Communicating Sequential Processes (CSP) model of concurrency.  

So far the best that I have been able to come up with is that the Actor Model allows the number and layout of nodes to change while CSP has a fixed structure of nodes.
I believe one core difference is that in CSP, processes synchronize when messages are received (i.e. a message cannot be sent from one process unless another process is in a receiving mode), while the Actor model is inherently asynchronous (i.e. messages are immediately sent to other processes' address, irrespective of whether they're actively waiting on a message or not).

There should be another answer that is more well-developed, however.