We won't get in to the bits and pieces of SSDs, and how they work on a mechanical level, but here is what SSDs are, and how they stack up to the more established hard disk drives (HDDs).
SSDs leverage new data storing mechanisms that allow it to retina data for a longer period of time, operate much faster than traditional HDDs and also more quietly and power efficient. But how is this possible? Does HDDs have any advantages over SSDs?
Solid State Drives are able to retina data for longer periods of time, and much more reliably, because it has no moving components and are not affected by magnetism. Hard disks have a spinning mechanism that is essential to retrieve data from the drive. Every time you copy or open a file from your HDD, the spinning disc that magnetically contains all your data, also known as a platter, is sequentially read as it spins a few thousand times a second. SSDs on the other hand do not have any moving parts; there is no spinning, and therefore no magnetic disc that stores all your data. It is through these physical differences that SSDs are able to operate more reliably, subject to much lesser chances of data loss and also remain unaffected by strong magnets!
But those are not the only benefits. Because there is no moving parts, SSDs also are more power efficient, as the electricity normally used to spin the platter, is simply not required. Besides that, quietness, is an advantage that SSDs leverage over hard disk drives: with no moving parts, one can imagine that little to no noise will be generated!
Hard disk drives however currently hold the advantage of affordability over solid state drives. Although SSDs provide immense advantages in terms of reliability, power efficiency, etc the process used to manufacture costs much more than those that manufacture HDDs. A typical 1TB HDD will cost under $100 if you look in the right places, however, a 1TB SSD currently costs around $500. Hard disk drives also have the advantage of availability of storage. Today, hard drives can range from 1TB to 6TB+. However, SSDs are only know to have storage space at maximum of 4TB, and a SSD of that size is known to cost thousands of dollars.
However to make the best of both worlds, something called fusion drives are known to exist. Fusion drives combines the speed of SSDs with the affordability of HDDs in to one hard drive. Fusion drives have an SSD cache will allows read/write operations to the drive to nearly reach speeds of pure SSDs, yet at the same time, giving you the affordability and availability of storage. A 6TB drive that has speeds of up to 300+mbs costing under a thousand will definitely be a great deal!
So there you have it, solid state drives vs hard disk drives and the best of both worlds: fusion drives.