Computers need at least two kinds of memory storage: volatile storage and non-volatile (NV) storage. Both are measured in bytes … but more commonly in kilobytes (one thousand bytes), megabytes (one million bytes), or gigabytes (one billion bytes). Volatile memory is typically called RAM (Random Access Memory). It is volatile because its contents are lost when the power is turned off. Non-volatile memory storage keeps its contents, even when the power is off.
Before getting more technical, I’d like to share the metaphor I like to use for these two kinds of memory. Volatile memory (RAM) is like the top of a desk … a “working space” for the files you are currently working on. Alternatively, non-volatile memory is like a filing cabinet … a space for your files when you aren’t working on them (i.e. when the computer is off). During normal operation, files come out of the filing cabinet, onto the desktop to work on them, and back into the filing cabinet for long term storage.
Examples of NV memory are your system’s main RAM, your CPU’s cache RAM, and your GPU’s (graphic processor’s) onboard memory.
An example of non-volatile storage is a hard drive (HDD): a set of spinning disks that store data using magnetism. These have served us well since the 1950s, but in 1991 we started seeing a new kind of NV storage called a Solid State Drive (SSD). Solid state drives store data using non-volatile RAM … NAND flash storage made up of floating gate transistors. They are much faster at reading and writing data than spinning magnetic hard disks, and there are no moving parts to wear out or get bumped. They are very dependable and offer a very long lifetime by allowing you to rewrite them millions of times before they reach their end of life.
HDDs and SSDs can be used on the same computer; we typically store the frequently-used data on the SSD, and the rest on the HDD. Hybrid HDD/SSD drives (called SSHD) exist, but they didn’t quite leverage “the best of SSD with the best of HDD” like we had hoped, so they have fallen out of favour.
SSDs are more expensive than HDDs, per unit of storage … but well worth the upgrade to get a read/write speed increase of about ten times. If a computer has a fast-enough processor to justify the upgrade, migrating a computer to SSD is a very good option to speed things up.