let say i have two tables called user and cart
user-table id username password 1 dave dave 2 dan dan cart-table id user-id item_name 1 2 car 2 2 table 3 1 laptop
now i understand that bother id's will be primary key.
i can also create user-id f-key bc its same as id from user.
but i dont understand the need for f-key. lets say i need to see who brought a car.
cant i just get user-id from cart. than look at id from user table and see the username?
does f-key some how makes it easier?
iam new to f-key