Why Diodes conduct current in one direction only, so the package must show which end is the cathode (the negative end, where the arrow of the schematic symbol points and where current exits in forward conduction). Manufacturers mark that end with a band or stripe printed around the body. The unmarked end is the anode.
Watch out Letters like C or K are used for the cathode in schematics and datasheets, but they are not printed on small diode bodies, and there is no room to spell out a word on a typical glass or plastic package.
Stripe = cathode, and the schematic symbol's bar is the same stripe. Band matches the bar.