JSF Features:

JSF is rich featured that make it much popular than
the existing frameworks. Some of the JSF features are :

I JSF is standard web user interface framework for Java.
II Built on top of Servlet API.
III JSF is a component framework
IV UI components are stored on the server.
V Easy use of third party components.
VI Event driven programming model.
VII Events generated by user are handled on the server.
VIII Navigation handling.
IX It can automatically synchronize UI components.
X JSF supports multiple client devices.
XI JSF has extensible architecture.
XII International language support.
XIII Extensive tool support (Sun, Oracle, IBM etc.).
XIV Rapid application development approach.

How JSF Fits For Web Applications?

JSF best suits the java web development environment
because of following reasons described below:

Easy creation of UI:

It makes easier to create complex UI for an application using JSF tags. Its APIs are layered directly at the top of served APIs that enable us to use presentation technology other than JSP, creating your own custom components and rendering output for various client devices.

Capacity to handle complexities of UI management:

It handles cleanly the complexities of UI management
like input validation, component-state management, page
navigation, and event handling.

Clean separation between presentation and logic:

One of the greatest advantages of JSF is its ability to
clearly separate behavior and presentation with in an
application. JSF is based on the Model View Controller
(MVC) architecture.

Shorter development cycle:

The separation between logic and presentation
enables a wide range of users (from web-page designers
to component developers) to focus on their own task
only, resulting in division of labor and shorter development
cycle.

Standard Java Framework:

JSF is a Java standard, which is being developed by
Java Community Process (JCP). Several prominent tool
vendors are members of the group and are committed to
provide ease to use and productive development environments for Java Server Faces.

An extensible architecture:

JSF architecture has been designed to be extensible.
Extensible means additional functionality can be given on
the top of JSF core i.e. we can customize the functionality.
JSF UI components are customizable and reusable elements. You can extend standard components and create your own complex components like stylish calendar,
menu bar etc.

Support for multiple client devices:

Component developers can extend the component
classes to generate their own component tag libraries to
support specific client. JSF’s flexible and extensible
architecture allows developers to do so.

Flexible rendering model:

Flexible rendering features separates the functionality
and view of the component. So we can create multiple
renderers and give them different functionality to get
different appearance of the same component for the
same client or different.

Support for Internationalization:

Java has excellent support for internationalization. It
allows you to localize messages with user specific locale.
A locale is a combination of a country, a language, and a
variant code. Java Server Faces adopts this property and
lets you specify which locale your application needs to
support. So you can display messages in different languages.

Robust tool support:

There are several standard tool vendors like Sun Java
Studio Creator which provide robust tools that take
advantages of JSF to create server side UI easily.