I think they were trying to say if you had a normalized database where instead of repeated varchar fields, you had a foreign key — that would act like a diction

I think they were trying to say if you had a normalized database where instead of repeated varchar fields, you had a foreign key — that would act like a dictionary. CREATE TABLE customer( id SERIAL, name VARCHAR(1024), status VARCHAR(1024) ) Vs CREATE TABLE customer( id SERIAL, name VARCHAR(1024), status INT REFERENCES status(id) ) CREATE TABLE status( id SERIAL, name VARCHAR(1024), ) It wasn’t very clear from the parent above, but I think this is where they were trying to go. The normalized version is smaller because you’ve swapped a repeated varchar ‘status’ for an int — so that’s effectively a dictionary. It’s not entirely correct, but it’s not that far off.