What is the difference between cannon, howitzer and smoothbore?

Howitzers have a smaller barrel and caliber, and are generally shorter than cannons, which usually have a barrel 20-30 times their caliber. Cannon body tube is long, usually more than 40 times the caliber. Howitzer muzzle velocity is small, cannon muzzle velocity is large, suitable for direct aiming and firing at tanks, infantry fighting vehicles and so on. Howitzers have a short range and are suitable for shooting horizontal targets. Cannons have a long range and can not only attack active targets on the opposite side, but can also shoot at sea targets. But modern technology has been merged into one, called the howitzer, the current active large-caliber artillery is basically a howitzer.

Smoothbore and smoothbore guns are distinguished by the presence or absence of rifling in the barrel --- those with rifling are called smoothbore guns, those without rifling belong to smoothbore guns (these are the two main categories, and no matter what else is an offshoot of these two categories, there is no third category parallel to these two categories). Before the nineteenth century guns were smoothbore guns or smoothbore cannons but the accuracy and range was pathetic, e.g. a smoothbore gun basically had to aim for the stomach at dozens of meters to hit the shoulder. The spiral rifling could stabilize the direction of the bullet flight to improve the range and accuracy, but the speed of the bullet out of the chamber decreased. So after the twentieth century smoothbore guns were abandoned only mortars do not need to consider the long range and other reasons to use smoothbore, until the 60's new technology and new ammunition support tanks to resume the use of smoothbore guns.