Why Build is needed? : <p>I am highly confused as why Build is needed in a java project.</p>

<p>I am new to Java. I have created a Java project which creates volume file.
I have run this code on my machine and created a JAR file and batch file which executes this JAR. 
Now who ever needs it, I hand over the JAR file along with .bat file and it is good to go.</p>

<p>Where some one asks me source code, I give them via SVN.</p>

<p>In this process I couldn't relate what BUILD means and where it is actually needed? And why we need build tool like Maven  (I know what maven is but can't relate)
I can easily share my JAR files and libraries with anyone who needs it.</p>
