Okay, imagine you have a toy box with a lot of toys in it. Now, you can't just put any toy anywhere in the box. You have to make sure they fit properly and that they won't break.
In the same way, mathematicians have something called a Banach algebra which is like a box for mathematical objects called functions. These functions are like toys that you can put in the box, but they have to follow some rules.
An amenable Banach algebra is a special type of box that lets you put your functions in nicely and it won't break any of the rules. It's a really good box to have because it's easy to work with and you can do lots of cool things with it.
So, think of it like having a great toy box that doesn't break any of your toys!