Killing horizon

A killing horizon is a special part of space around a very heavy object, like a black hole. It's like a big invisible wall that marks the point of no return. Think of it like a kid jumping off a diving board into a swimming pool - once they jump, they can't change their mind and go back to the diving board. It's the same with the killing horizon and objects that get too close to a black hole. Once they cross that invisible line, they are stuck and can never escape the black hole's super-strong gravity. Imagine being in a rowboat heading towards a big waterfall - once you get over the edge, you can't paddle hard enough to get back upstream. Same idea with the killing horizon and a black hole. It's not a good idea to get too close!