ANT stands for Another Neat Tool. It is a Java-based build tool from Apache. Before going into the details of Apache Ant, let us first understand why we need a build tool in the first place.
Need for a Build Tool

On an average, a developer spends a substantial amount of time doing mundane tasks like build and deployment that include:

Compiling the code
Packaging the binaries
Deploying the binaries to the test server
Testing the changes
Copying the code from one location to another

To automate and simplify the above tasks, Apache Ant is useful. It is an Operating System build and deployment tool that can be executed from the command line.
History of Apache Ant

Ant was created by James Duncan Davidson (the original author of Tomcat).

It was originally used to build Tomcat, and was bundled as a part of Tomcat distribution.

Ant was born out of the problems and complexities associated with the Apache Make tool.

Ant was promoted as an independent project in Apache in the year 2000. The latest version of Apache Ant as on May 2014 is 1.9.4.

Features of Apache Ant:

Ant is the most complete Java build and deployment tool available.

Ant is platform neutral and can handle platform specific properties such as file separators.

Ant can be used to perform platform specific tasks such as modifying the modified time of a file using 'touch' command.

Ant scripts are written using plain XML. If you are already familiar with XML, you can learn Ant pretty quickly.

Ant is good at automating complicated repetitive tasks.

Ant comes with a big list of predefined tasks.

Ant provides an interface to develop custom tasks.

Ant can be easily invoked from the command line and it can integrate with free and commercial IDEs.