Or do you mean the package prefixes java and javax? Most of the packages starting with javax where initially additional libraries not shipped with the JRE / JDK (e.g. Swing); they were later integrated. Package javax.activation is one of the latest packages to be included, after spending much time as part of the Java Activation Framework.
No I am talking about Javax only.
I have read that it is also a package or just another naming conventation but not sure about it.
Hence I am asking for more information on it.