It is related to Object Oriented Concept. Here we are 
distinquishing wt are all the acivities to be done and list 
of actors(objects)who wil interfere with those activities. 
    It is a technique for capturing functional requirements 
of systems and systems-of-systems.

when v use a use case that is use case

use case is a informal or formal description, to understand 
how the user will be using the application.

HI 
   Murali

Use Case is a document that describes the functionalities or
operations of the software  with "SET OF SCENARIOS" 


sun_ramprasad@yahoo.com

Each use case provides one or more scenarios that convey 
how the system should interact with the users called actors 
to achieve a specific business goal or function. Use case 
actors may be end users or other systems. Use cases 
typically avoid technical jargon, preferring instead the 
language of the end user or domain expert

It is a graphical representation of a requirement

use case: how to use a functionality is called as usecase
prepared by the bussiness analyst people

Use case is a diagramatic representation of requirements
, Actors and their relationship will be clear understood 
with this diagram. so that the tester can easily understand 
the requirement.

for eg.   customer(n)------->Account

customer can have n number of account.

please correct me if im wrong.

when the testing team is expected to perform a testing on 
one of the business critial application then identification 
of TC may not be effictive and realistic now using use case.

U C is tells the user defind description which explain how 
the soft ware would be used by the end user in reyality. 
from every given U C we may identify the alternative floats 
or multiful ways of performing the same operation which 
will help us to identify more senarios.

THIS IS MY OPENINE OF U C ANY MISTAKES IS THEIR PLZ WRITE 
BELOW.

The SA uses the BRDS & SRDS to prepare the navigational 
flow of the workings of the application in the form of USE 
CASES. It gives a rough picture of the enire system.

Use case is a map or flow between the system and the end 
user.it contains pre conditions, post conditions and 
expressions of a test.
it can be prepared by the Test lead or Development lead