CZ stands for Ceska Zbrojovka ( Czech gunmaker, or "arms maker" )
CZ was founded in 1917, and has had several factories.
Brno denotes the Brno factory, in the large ancient city of Brno.
VZ is an abbreviation of vzor ("model"), like "Vz-24.
The Germans set up Mauser factories in Czechoslovakia and Yugoslavia to build small arms in circumvention of the Treaty of Versailles. So lots of the CZ rifles are in the M-98 long rifle of WWI, and the later K-98 (kurz) short rifle of WWII.
After the war, they produced a very smooth, sleek Mauser variation, the ZG-47, upon which the 21 and 22 models were built. Later models were the 600, 601 and 602, larger framed Mausers. Today's CZ-550 is an updated sporting Mauser derivative, not quite as smooth as the 600 series, and certainly not the ZG-47, but with excellent barrels, and the actions will smoot in with use. They are one of the few barrel makers still hand honing and polishing the rifling as a final step.