Magnetic storage is what most people think of when they think of computer storage. It is the most popular form of storage for electronic devices and it is also the cheapest. Everything from your camera to phone uses magnetic media. For a very reasonable price you can get multiple gigabytes of space on a consumer disc no larger than the head of a thumbtack. Its portable and easy to use.That comes with a trade-off though; magnetic storage is notoriously impermanent. It is great for short term storage or transferring files from your devices but it will not survive long term storage reliably. External and internal drives are the way most of us store our files on our computers. I use a 2 terabyte external drive for my main computer all my files and photos are kept there and not on the internal computer drive. That drive is roughly the size of a large smart phone and uses USB connectivity.
You can now get 6 terabyte drives although 2TB to 4TB are more common. A good 2 terabyte drive is less than $100 USD at the time of this writing with 4 TB drives around $150 USD. Computers that are a couple of years older have trouble recognizing more than 2 TB drives sometimes so make sure you check your model and manufacturer to see if you can use the bigger drives. For most artists a terabyte is more than enough for a year of images even for digital work. That would be roughly equal to ten thousand 100 MB files.
I swap my external drive with a new one every year or so. I keep the old ones after transferring the information to optical media for more permanent storage. So far these kinds of drives seem to last about ten years before the files show serious signs of corruption which renders most of the information unreadable but I have also had drives that became unreadable in just a year or two. It is always smart to keep important things in more than one place and really important things in hardcopy.