General Understanding Of Relationships

Please see the attached two files.

I have tried to figure out what the difference in functionality would be between 1 and 2. In the latter I have just created a series of relations between the last two tables (but that structure could be used throughout the whole DB instead of hanging it together with one relation between tables as is the case for the rest of the DB in this picture).

So there can be three different situations with this table structure:
- linking all tables together via multiple relations
- linking all tables together via a single relation
- a combination of both, such as in the images.

Why would someone choose one versus the other? "Which is better in what situation?"

I've been fiddling about for a while now, but in a structure such as this it doesn't seem to make a difference. Or maybe there are differences in use/design, but on a level that I have not explored yet.

Could anyone explain this to me a bit? I have multiple books, all of which handle basic relations but I have not yet seen an explanation for this question. I think understanding the whole relationship topic is critical to be able to see other pieces of the puzzle fall into place later on. And as of yet, this is really fuzzy to me.