Monkey testing is when you give a monkey (or a computer program acting like a monkey) a task to complete randomly. Just like how a monkey randomly jumps from tree to tree without any specific reason, monkey testing makes your computer program do things in a random way.
When a computer program is being developed, it needs to be tested to make sure it does what it's supposed to do. Monkey testing is a type of testing where the computer program is poked and prodded randomly to see what happens. For example, if your program has a button that is supposed to open a new window, monkey testing might try clicking the button many times, or click it multiple times quickly, just to see if it opens a lot of new windows.
Monkey testing helps to find any unexpected errors or problems in the program. It can provide insight into how the computer program reacts to unexpected user behavior or input. Monkey testing can help find problems that are hard to replicate otherwise, and sometimes find problems you didn't even know existed!
So, just like how a real monkey explores its environment curiously and randomly, monkey testing lets your computer programs "explore" and find any problems that might exist randomly too.