Message - A method of communication between processes. Timeout - Mechanism for waiting for a given time period. Registered Process - Process which has been registered under a name. After Pid2 is process identifier of the new process - this is known only to process Pid1. From and Msg become bound when the message is received.
Messages can carry data.
Messages can carry data and be selectively unpacked. A and D become bound when receiving the message. If A is bound before receiving a message then only data from this process is accepted. The first message to arrive at the process C will be processed - the variable Msg in the process C will be bound to one of the atoms foo or bar depending on which arrives first. A and B are local bound variables in the process Call .