yes ik its empty but im just curious that i found an adress that HAD been used
If you check some you will find that there are a lot of address that have been used but the total balance is always 0.
why does that happen
That user does not know what they are talking about. I'm no expert but my understanding is that private keys are a number, and that the amount of possible private keys that there could ever be is just under 2^256.
If you want to understand just how safe that amount is, please refer to
this video, which will explain just how long it would take to calculate the private keys with the greatest supercomputer ever.
Now what you need to understand is that when you have a ridiculously large amount of possible numbers that could ever be created, there are also very small numbers. An example of a very small number is 1. People can use any private key to access their coins, and therefore people with poor wallet software or people who created their private keys themselves could use the number 1.
Any normal wallet software will randomise your private key, which
extremely close to 100% of the time results in a crazily large number that no one will ever calculate. The chance of that not happening is so low that you can safely ignore it, as can everyone in the world.
The first page on directory.io is showing the private key numbers 0 to 127. Because those numbers are extremely low, someone has decided to use them as their private key, either as a joke or because they're extremely dumb. Of course people know those private keys, so they steal funds from them and the balance is 0.
What you don't understand is that directory.io is in fact not a database. It just generates the private keys' addresses when you go onto each page. But you can never go through any noticeable amount of the pages.
Security test: type in an extremely large random number (for example, 947184818258275825772489752923525971841411113849). You should put it into the domain like directory.io/947184818258275825772489752923525971841411113849. Now look at the addresses. Have any of them been used? No. No currently existing computer would find funds created using decent wallet software, ever.
