Carburetors - Spreadbore and Squarebore

What are spreadbore and squarebore carburetors?

In cruising and driving cars, a spreadbore carb will provide better fuel economy and driveability due to its smaller primary openings, while providing the large CFM needed for max power when the large secondaries open up.

A spreadbore carburetor (think Quadrajet) has smaller primary barrels and larger secondary barrels.

A squarebore carburetor (think Holley) is a 4 barrel carburetor with each barrel having the same diameter.