A generic question: Schema without foreign key specification?

Dear group,
 While designing 3-4 different schemas for my
database, a question has been chasing me. I am not a
CS graduate and I was never taught the nitty gritty's
of Dabase schema or rules.

My question is - a schema that has no foreign key
defined (except in 1 or 2 instances), will it be
considered a good schema or bad schema by experts.

Imagine a scenario where most of the relations are
defined by linker tables(relationship table) that is
formed by two different primary keys from two
different tables are defined to avoid foreign key
relationships. creating a database in this kind of
scenario, can it be considered a good database design.


I hope it is not a stupid question. If it is please
excuse my ignorance.

Thanks
Kumar.

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