What is a JAR file in Java?
A JAR (Java ARchive) is a package file format typically used to aggregate many Java class files and associated metadata and resources (text, images, etc.) into one file for distribution.

How do I run an executable JAR file?
If you have a jar file called Example.jar, follow these rules:
1.Open a notepad.exe.
2.Write : java -jar Example.jar.
3.Save it with the extension .bat.
4.Copy it to the directory which has the .jar file.
5.Double click it to run your .jar file.

What is the manifest file?
The manifest is a special file that can contain information about the files packaged in a JAR file. By tailoring this "meta" information that the manifest contains, you enable the JAR file to serve a variety of purposes.