Ah, projectiles. Nothing says “festive” like launching various objects through the air. The tradition of shooting stuff at other stuff is deeply rooted in human society, and nothing does it more spectacularly than a cannon.
Nowadays, nobody really refers to cannons as “cannons”. They’re typically called “artillery,” “guns,” or “mortars”. Either way, people get really creative with the stuff they shoot out of them.
The earliest cannons were a little odd. They were typically filled with large clusters of arrows, which would hopefully not shatter to bits before being launched toward the enemy. It took a little while to figure out that shooting stuff with a good, solid weight to it tended to work better. This idea evoked two basic kinds of projectiles: shot and shells.
Shot is a solid projectile designed to rip holes in stuff, like buildings and boats and people. One of the first types of shot they came up with was canister shot (called grapeshot if used at sea). Canister shot is a pile of small metal balls — basically a much larger version of what’s in a shotgun shell. Naturally, it causes a lot of damage, both to people and to structures. There’s also the classic cannonball, which rips a giant hole in whatever it hits. The cannonball was a classic favorite for all kinds of warfare, and it eventually evolved into shells.
Shells work differently than shot. Shot is meant to just rip stuff apart, but shells explode. They are filled with gunpowder or whatever else people can use to make them self-destruct. The hope with shells was that they would explode close to their target, although they often blew up in midair, as described in the American national anthem: “And the rocket’s red glare / The bombs bursting in air”. Recently, shells have gone beyond just blowing up. The incendiary shell was invented in 1460 and designed to start everything it touched on fire. In 1543, the English filled them with something they called “wildfire” which may have been similar to Greek fire — a now unknown substance which burned constantly and could not be extinguished. Sometimes shells would be filled with molten iron to ignite ships. There were also shells called star shells or lightballs which were shot high into the air to illuminate the battlefield. Shells could also be filled with smoke to disorient the enemy or poison gas to force them into the open. Some shells were even filled with shrapnel — anything from canister shot to broken glass or coins — to cause maximum damage to humans upon explosion. 70% of the injuries in World War I were due to shrapnel shells. Many injuries occurred during attempts to dispose of unexploded shells.
And of course, there’s always the option to be a really nice person, like the Boers at the siege of Ladysmith on Christmas day in 1899, who fired a fuseless (read: nonexplosive) carrier shell into Ladysmith containing a Christmas pudding, two Union Jacks, and a message which read “compliments of the season”.