Shared Memory
Refers to the memory part of a computer system in which the memory can processed directly by any of the processors in the system.
Distributed Memory
Refers to network based memory in which there is no general address space for the a variety of memory modules consist of the memory system of the (networked) system. Generally, a processor or a collection of processors have some memory module connected with it, independent of the memory modules connected with other processors or group of processors.