What are Attributes in Clustering
 

Hi Buddies,
I am learning CLUSTERING in LINUX for the first time. I came across following terms:

getcustomattribute - Get a custom attribute for system(s)
listcustomattributes - List custom attributes for system(s)
removecustomattribute - Remove a custom attribute for system(s)
setcustomattribute - Set a custom attribute for system(s)

Can anybody please tell what exactly the attributes in clustering signify.