I am trying to learn spring as I am new to it. I have a doubt with regards to the spring jar files. Why do some jar files end with 'x.y.z'? Does it denote anything? I mean what is the difference between org.springframework.asm-x.y.z.jar and a org.springframework.asm-3.1.0.M2? Hope someone can explain, Thanks.
Those are version numbers. The latest version of Spring is 3.2.3.RELEASE. You want to use the same version of Spring across all components do not mix and match them or you will have issues. Typically you should use Maven or a similar tool to manage this type of thing for you, you just assign a property in the POM with the version to bring in and reference that property everywhere (I suggest using the latest version).
edit* I just re-read your question and now I am confused, all the jars should end with .jar. Can you provide a link to what it is you are talking about?