Polandball is a type of internet meme, where people create funny cartoons using drawings of different countries represented as round balls, with their national flags on them. These balls are then given humorous personalities and national stereotypes, which they use to interact with other countries balls in silly, exaggerated ways.
The idea comes from the fact that many countries' flags are simple shapes that can be easily represented by round balls, and people find it funny to see these countries interacting with each other in silly ways. For example, you might see a ball representing Russia wearing a big fur hat and talking with a strong accent, while a ball representing America might have a big hamburger and talk loudly.
The humor comes from the different ways each country is represented, as well as the ridiculous situations they find themselves in. Sometimes, people use Polandball to comment on current events or political situations, using the characters to represent different countries' opinions or actions.
Overall, Polandball is just a silly and fun way for people to create and share funny cartoons using national stereotypes and humor.