Difference between Block-related and Symbol-related messaging in Step7

Dear Forum Members,

I am looking for document for complete understanding the difference between Block-related and Symbol-related messaging in Step7 with little more examples. It would be useful if any one share the basic document for the same.

I got the few document from the support portal, But not sufficient for complete understanding about the chronological messaging.

It would be useful if that technical document covers the Block-related and Symbol-related messaging with some example.

And finally, is it possible to use the Block-related messaging for alrming process state change? and what are synchronous event with examples..

Thanks for your time.

Rajan.