How and when web services should be used? Any specific scenarios or examples please?

The application that I am going to develop is called ticket booking system what can be the use of Web Service to use here.


Ticket Booking......a nice concept......
in webservices we can create methods....n call that methods in our application Remotely.....(Remoting and Webservicesare the different scenarios.....)

The use of Webservices in ur application....is like by using webservices we can check...number of Ticket are booked....n how much are pending....n lots of more.....its all depend upon the user Requirement

Web services are used when you want to allow multiple ussages of diffrent subset finctionalities.
For example if you provide a webservice to find what is the number of remaining seats.
This webservice is a complete business flow and can be used in various other applications to show from your system how many seats are still available, i.e even out side of you application.

If you are familiar with Remote Function CAlls Webservice is just the same wiith additional infrastructure to support authentication, discoverability, ease of use, etc etc.
It would be good if you read through
a simple enoguh intro thru:-
the main idea is to have enterprise ready systems ready for integration and is the way of now and the future.

For your simple project i would advise you to use REST style webservices rather than the Bulky SOAP implementation.
So just google around and you should be happy.