Dupe of NAT

NAT provides association between nodes & terms,
when creating a node, NAT creates a term associate with node

"One Node per Term" module allows only one node to be assigned to a term.

example
if you have a term tid = 15 named feature and assign node (nid=35)
and after go to assign another node (nid=40) to term 15 (feature)
module "One Node per Term" will unassigned first 35 from term 15 and after will assign node (nid=40) to term 15
allowed only One Node per Term