NV-RAM (Non-Volatile RAM) is basically memory that keeps its data even when the power is turned off. That’s the key difference compared to regular RAM like DRAM or SRAM, which lose everything as soon as power is gone. It’s still random access memory, meaning the system can read and write data quickly, unlike traditional storage such as hard drives. A common example people are familiar with is flash memory, which is non-volatile and widely used today.
Non-volatile random access memory (NVRAM) is the general name used to describe any type of random access memory which does not lose its information when power is turned off. This is in contrast to the most common forms of random access memory today, DRAM and SRAM, which both require continual power in order to maintain their data. NVRAM is a subgroup of the more general class of non-volatile memory types, the difference being that NVRAM devices offer random access, like hard disks.
The best-known form of NVRAM memory today is flash memory. Some claim flash memory to be a truly "universal memory", offering the performance of the best SRAM devices with the non-volatility of Flash. To date these alternatives have not yet become mainstream.