A Zettelkasten is an archive of notes which extends your mind just like a hammer extends your arm.
A Zettelkasten can extend your memory. It grows as you learn and as you store your knowledge inside of its archive. You need to make thoughts tangible by writing them down so you can continue to work with them in the future. That’s because you probably can’t reproduce every single thought you ever had when you need it. You need to capture them before they fleet away. When you capture a thought on a note, you can come back to it later. If you also care to put it into an archive, it’s accessibility is future-proof. In this respect will a Zettelkasten extend your memory: it offers a safe storage for your thoughts and for what you learn.
With a Zettelkasten your mind will blow your mind, as my good friend Sascha likes to say.