Fill or kill

Okay, imagine you go to a candy store with your Mom and you really want to buy some gummy bears. Now, fill or kill is like a special way to buy gummy bears (but instead of gummy bears, it's about buying stocks, which are like little pieces of a big company that you can own).

To help you understand, let's pretend that the candy store has a limited supply of gummy bears and you really want to make sure you get some, but you only have enough money for 10 gummy bears. Fill or kill means that you tell the person at the candy store that you want 10 gummy bears right away, and if they can't give you all 10 gummy bears at the exact same time, then you don't want any gummy bears at all.

Now when it comes to buying stocks, fill or kill means that you tell someone (like a broker or an app) that you want to buy a certain amount of stocks right away, and if they can't give you all of the stocks you want at the exact same time, then you don't want any stocks at all. This helps you make sure you get what you want and you don't have to wait around for more.

So, fill or kill is like a way to quickly buy or sell things (like gummy bears or stocks) and make sure you get exactly what you want all at the same time.