Create/Show relationship between parent and child term in Drupal Taxonomy

Possible Use-Case : You want to show a list of "Countries" and there related "Cities". But you want only related cities to be shown on the page .
 To do this place country as parent term and all the cities as sub-term. So construct a vocabulary like this :

INDIA 
- Delhi
 - Rajashtan
- Chandigarh
- Gujrat

USA
- Alabama
- Alaska
- Georgia
- Illinois

Then use simple module called "Simple Hierarchical Select" https://drupal.org/project/shs or you can also use "Hierarchical Select" https://drupal.org/project/hierarchical_select
But hierarchical select has more functions but if you have taxonomy related task only then you can use only SHS as for the above use-case.

Now go to the content type -> manage fields -> select term reference-> simple hierarchical select Or create a field like this if you haven't created.
Now go to your views or create a view if you haven't already created => select the "your-field-name" (hierarchical select ) from filters and force it to some depth. Expose this filter for users.

Then it will show first country name and then child term which are city names.