The focus of this training program is to provide functional training that is why I have presented list of tables and the relationship between them.
Two things I would like to say:
1) In order to find out tables behind a certain screen, simply navigate to the screen, query all the records, then navigate to Help->Record Hitory, the table name will appear on the popup window along with other userful information.
2) You can refer to Technical Reference Manual for list of tables in a certain schema.
Just keep in mind the broad objective. If you are exploring tables and its data through back end but then make sure you have some objective to meet otherwise you will be lost in details and you will loose out on time you could have spent on learning functional side of things.