Hadoop can be run in 3 Modes :

Standalone Mode

Pseudo-Distributed Mode

Fully Distributed Mode

In Standalone Mode, there are no daemons running.

In a Pseudo-Distributed Mode, Daemons run locally, simlulating a cluster on a small scale.Its easier to set up Hadoop in Standalone and pseudo-distributed mode.

In a Fully Distributed Mode, Daemons run on a cluster of machines.