As explained in the Producer Help - Templates section of this Help file, Layouts can contain one ore more Pages. If you are running a Go, or Premium edition, only one layout is allowed. When running a Professional or Ultimate editions, you can use multiple layouts within your template.
Layouts are very powerful as they offer you the possibility to change based on information out of the connected database. Also each layout can have it's own setting like for example, no magnetic encoding or magnetic encoding.