The "Old European Emperor" and "Big European Emperor" in Genshin Impact both refer to the player's luck when drawing characters in the game.

First of all, let’s explain the concept of “European Qi”. In the gaming community, "European Qi" refers to a state of good luck, usually used to describe a situation where there is a high probability of obtaining rare items or characters in a draw game. The "European Emperor" refers to a player with excellent luck.

In Genshin Impact, character extraction is mainly done through the prayer system. Every time you pray, you will have a certain probability of getting a 5-star or 4-star character. This probability is fixed and is not affected by personal luck or status. So, in theory, every player has the same chance at drawing a character.

However, due to the uncertainty of luck, players may have good or bad luck when drawing. Some players may have drawn multiple rare characters and are called "European Emperors", while some players may have never been able to draw their favorite characters and are called "Africans".

As for the difference between "Old European Emperor" and "Great European Emperor", these two terms do not have an exact definition. They may be concepts derived from the player community. Generally speaking, "Old European Emperor" may refer to an old player who is lucky enough to have drawn many rare characters in the game. The "Great European Emperor" may refer to a player who has drawn a particularly precious and super rare character in the game.

It should be noted that the above is only an explanation of the potential definitions of "Old European Emperor" and "Great European Emperor", and the specific definitions and uses will still vary depending on different player communities.