Types of common System XML
Library.xml: If we want to share a single piece of code
across multiple applications, we can’t copy paste the same code in all
applications. To consolidate the common code we have Library xml
Ex: Suppose if I want to display a dialog in so many
applications, you just put the code snippet in library.xml and refer that code
snippet ID in all the applications where ever you want.
Menus.xml:
Common menus across all the applications
Lookups.xml:
With this you can look for a list of values. Like persons, classification etc.