Okay, so let's say you are playing a game where you have to catch butterflies in a garden. But there are a lot of things flying around in the garden, like bees and moths and other insects that you don't want to catch. You only want to catch butterflies.
This is kind of like a filtering problem in stochastic processes. You have a bunch of things (like data or signals) coming at you, and you want to pick out the ones that you are interested in (like a particular signal or piece of information).
Just like in the game, the problem is that there are things mixed in with what you want that you have to filter out. But sometimes, the things you want are hard to distinguish from the other stuff, and it can be tricky to catch only what you're looking for.
So, like a butterfly collector, you use different tools to help you catch the things you want and filter out the things you don't. In a filtering problem, mathematicians and engineers use things like algorithms and statistical methods to try to separate the signal they want from the noise.
Overall, the filtering problem is all about sifting through a bunch of information to pick out what you're interested in, just like catching butterflies in a garden.