Characters
A font is a style of writing the letters in the alphabet - or Chinese characters. Fonts should really be called typefaces. But most people today just say font.
In the very old days, before printing, people wrote out books by hand. But around 1450, in Germany, Johannes Gutenberg developed the first printing press. The typeface - all the letters - were made of lead.
Meanwhile in China
In China there was a typeface 400 years before Gutenberg invented the press. The letters were made of ceramic. But it was not used much because it was too difficult. In China, for a long time, when something had to be printed, somebody had to carve a piece of wood with all the characters on it. If you covered the raised characters with ink and pressed it on paper, you had a woodblock print. You can do something similar at home with a potato.
Early fonts