it is used for software development, including XP (Extreme
Programming), and it advocates iterator development

Agile methodology is anadaptaive methodology, its people 
oriented. 
Here are some of the other characteristices of the Agile 
methodology. 
1. Delivery frequently. 
2. Good ROI for client. 
3. Test frequently. 
4. Collaborative approach.

Agile methodology is more of people oriented. Agile 
methodology helps us to increase productivity and reduce 
risks. There are 2 popular agile methods- Extreme 
programming (XP) and Scrum.

People believe that there is less documentation in Agile. 
But agile also includes documentation and it can be used 
either a small or a large projects. In agile Development, 
testing is also integrated throughout the life cycle. But 
for the testers, they will not have a good business 
requirement. So they have to get the details from the 
client or through the developer. The testers will do more 
of Quality Assurance work than testing.

 

 Agile Methodology- Characteristics

Ø  Frequent Delivery

Ø  More Iterations

Ø  Test frequently

Ø  Less defects

i refered the site www.sphur.com

Agile methodology is more of people oriented. Agile 
methodology helps us to increase productivity and reduce 
risks. There are 2 popular agile methods- Extreme 
programming (XP) and Scrum.

It is a methodology to satisfy the customer through early
and continuous delivery of valuable software. This is useful
when we dont have a clear idea of the client's requirements.
The development activities can be carried out using the
iterative actions

Agile is software development methodology. It is very 
effective where Client frequently changes his requirement.
Since it has more iteration so you can assure a solution 
that meets clients requirement.
More than one build deployement for a project.
It involves more client interection and testing effort.

There are two methods by which this methodology can be 
implemented:-

1- Scrum
2- Extreme Progamming

Scrum: Each iteration would called a scrum which can be a 1-
2 Months.In Scrum Client prioritise his requirements what 
he want first. If developer did not meets all the 
requirement which was being fixed for a perticular scrum 
than rest of the development part would be transferred to 
the next scrum (would be delievered in the next build),  
means developer cann't increase time decided for a scrum.
Its fixed.

Extreme Programming (XP): here iteration period would be 
less then in scrum , which is being 2-4 weeks.
Here developer prioritise what to do first on the basis of 
client requirement.
This duration which was being fixed for a iteration, can be 
increase if the some development part is still pending. 
The build would deployed with having all the client needs.
Thus iteration period is not fixed here it can be increase.
but iteration should meets all the client's requirement in 
this build.
More attension is required for testing in XP.

Agile software development is a conceptual framework for 
undertaking software engineering projects. There are a 
number of agile software development methods, such as those 
espoused by the Agile Alliance, a non-profit organization. 
Agile methods attempt to minimize risk and maximize 
productivity by developing software in short iterations and 
de-emphasizing work on secondary or interim work artifacts. 
Scrum and Extreme Programming (XP) are two of the most 
popular Agile methods, however, there are many more Agile 
methods and agility, as a conceptual framework, may also be 
applied to the execution of more traditional methods.

Apart from all the above answers, just add this important 
point.
There are many flavours of Agile Development:
1- Agile Manifesto
2- (XP) Extreme Progamming
3- Scrum
4- Crystal
5- Context Driven Testing
6- Lean Development
7- (Rational) Unified Process

Agile methodology is a conceptual framework where software 
is devloped in iterations. Each iterations has Requirement 
analysis, planning, design, coding, testing and 
documentation.
Characteristics :
 - Many builds are delivered in the iteration process
 - Accepts change of requirement at any stage
 - Requires close communication between business, 
Development and Testing people
 - Reduced risk and time to devlop
 - Less documentation work compared to other methodologies
 - Requires continious testing