Okay, so let's pretend you have a toy box full of toys. You can play with a doll or a toy car or a ball or a puzzle. But sometimes you might want to play a game where you pretend to be a spy or try to solve a mystery.
Now, imagine a big group of grown-ups who really like to play those spy and mystery games. They want to have special toys and tools to help them play those games better. That's what BlackArch is - it's a big group of grown-ups who like to play a special kind of computer game where they try to solve problems and find information.
They made a special toy box full of tools that can help them play the game better. These tools are called "hacking tools" because they can help the players find information that they might not normally be able to find.
But just like you have to play with your toys responsibly and not break them or use them to hurt other people, these grown-ups have to use their hacking toys responsibly and not use them to hurt other people or break the law.
So, in summary, BlackArch is a group of computer game players who want special tools (called hacking tools) to help them play the game better. They made a special toy box (called a Linux distribution), which contains all the toys. But it's important to remember that just like you play with your toys responsibly, these grown-ups have to use their toys responsibly too.