Idempotence is like making looking at a cake: no matter how many times you look at the cake, the final result is still just one a cake. Whereas a non-idempotent operation is eating a slice of cake. Every time you eat a slice of cake, you have less cake left, until you have none left.
In computing, idempotence means that if you perform an operation once or multiple times, the end result will be the same. This is particularly important in distributed systems, APIs and event driven architectures, where network issues or failures can cause operations to be retried.
For example, let's say you have an API endpoint for updating a user's email address. If the endpoint is idempotent, it means that no matter how many times the request to update the email address is sent with the same payload, the result will be the same as if it were only sent once. This is essential for ensuring data consistency and preventing unintended side effects.