Variables: Anonymous variables
Use anonymous variables to ignore the values you don't need. In Prolog, the anonymous variable is represented by a lone underscore ("_").The anonymous variable can be used in place of any other variable. The difference is that the anonymous variable will never get set to a value.For example, If you need to know which people are parents, but you don't need to know who their children are.
parent(Parent, _).
The anonymous variable matches anything.