Where is the Module, Application and the relationship between Module and Application information saved? In which tables in that information saved?

Information re Modules is saved in the MAXMODULES table.
Information re Applications is saved in the MAXAPPS table.
Information re the relationship between Modules and Applications is in the MAXMENU table. 

The example shown below is about the Work Orders module.

1. Module information about 'Work Orders'
Run the query below.

SELECT * FROM MAXMODULES WHERE DESCRIPTION = 'Work Orders'


The module for Work Orders is WO.


2. Which applications belong to the WO module ?
Run the query below. The applications belonging to the WO Module are then displayed.

SELECT KEYVALUE FROM MAXMENU 
WHERE MENUTYPE = 'MODULE' AND ELEMENTTYPE = 'APP' AND MODULEAPP = 'WO' 
ORDER BY POSITION


3. Information re the Application's name
Run the query below. The name of the applications belonging to then WO Module are then displayed:

SELECT APP, DESCRIPTION FROM MAXAPPS WHERE APP IN (
SELECT KEYVALUE
FROM MAXMENU WHERE MENUTYPE = 'MODULE' AND ELEMENTTYPE = 'APP' AND MODULEAPP = 'WO' )