The Hard Drives
HDD work with actual disks in the hard drive. When given power, these disks spin, kind of like a DVD or CD player. As these disks spin, a little needle goes over them, reading the data. The little needle has a head which can send out little pulses gets a signal on if the spot on the disk is magnetic in a certain way. To write information, it sets the magnetically on the spot on the plate to later be read. And there is a little more to it, like how the information is transported and processes, but that's the basics. A needle and magnetic pulls or pushes.
Solid state drives are a lot different. The reason they are called solid state is because there are no moving parts. The most moving thing is electricity. So everything is set 'solid' in place. You may not know, but you've used a small solid state drive and you didn't even know it! Something called flash memory is the real cause for SSD's. Flash memory is in included in Flash Drives/USB Sticks, SD cards, RAM, and of course the SSD. It took forever to find a resource to explain it well enough, and I'm not sure I can explain it well enough, but here goes nothing. The SSD is a big set of chips on a board. These chips have a logic gate called NAND. What is a logic gate? A logic gate is a part on a computer chip that when information flows in, a specific result comes out. For example, an AND gate gives an output when two inputs are given. So if you have electricity flowing through one input and not the other, the signal doesn't go all the way through. Another example is the OR gate. Basically, one OR the other has to be true to give an output. One more example is the NOT gate. The output is NOT, what is given. It inverts the signal. Not too hard. A NAND gate combines AND and NOT. Basically, if two inputs are true, with AND, it would say that it is true, but it is the opposite because of the NOT. Lost? It's okay. How the SSD works is that there are a ton of gates right next to each other. When writing data, electrons get stuck in a gate. When you read the data, a certain voltage is sent through the system, and if the current goes through, it is a true, but if it doesn't go through, it is a false. This is what I understand out of it, but it is simply electrons getting trapped and weather they are there or not.