What does cardinality for node stand for?

Hi all,

Im very new to ABAP web dynpro.just started building some sample applications.Can anybody explain me what is the meaning of CARDINALITY for node.What do the different values for cardinality of a node mean?How do I know when to choose what cardinality for the node when creating the node?PLease can anyone explain with proper examples.

Thanks.

BR,

SRM tech