Standalone (or local) mode:
F Default mode.
F You don’t configure anything else.
F NameNode, DataNode, JobTracker and TaskTracker,run in a single Java process.
A separate JVM is spawned for each of the Hadoop components and they communicate across network sockets, effectively giving a fully functioning mini cluster on a single host.
Fully distributed mode :
Spread across multiple machines, some of which will be general-purpose workers and others will be dedicated hosts for components, such as NameNode and JobTracker.