RAM

Reserved Memory
User Memory
Execution Memory (Working Memory) - Operations on data is performed here
Storage Memory (Cache) - Place where the result is stored. Not permanent storage

Static Memory

Execution Memory - 2GB, Storage Memory - 6GB (Example) (When cache gets full evict LRU block to disk) - Spark 1.0
LRU: Least Recently Used (Cache Management Policy)

Dynamic Memory

Execution Memory gets full it access more space of the Storage Memory and evict LRU block from Storage memory to disk - Spark 1.6 and above

Apache Spark Memory Management | Medium