If you’re a techie, you probably know that a hard disk drive is simplified a spinning platter with a moving head above it to read and write the data. This means that a hard disk has a lot of moving parts and this is also why SSDs are rapidly becoming more popular. The moving parts make a HDD more noisy, slower, less energy efficient and more susceptible to damages than SSD drives. Usually you don’t open a harddrive and it’s therefore very likely that you’ve never seen the internals of harddisk moving and operating.
But some guys going by the name ‘Slow mo guys’ have put a movie on Youtube which shows a hard disk in full action, in slow motion. And you’d better see it, so you can explain your kids in 10 years what those HDDs where and how they worked. Just like you probably need explaining on Floppy Disks, remember?