Explain difference between primary and secondary computer memory

I do not know which is the main memory. I want to find the difference between two memory of the computer. They are:

RAM + ROM

ROM = Read Only Memory = Read-Only Memory

Random Access Memory = RAM = Random Access Memory.

The ROM contains all the system resources required to operate and read at the beginning and every time you need the system. The RAM is used by normal applications, all programs that start and stop, etc.. What is the difference here if we get upgrade on the same.

The secondary memory is designed to overcome some limitations of main memory. It is non-volatile, meaning retains its contents even when power to the computer system is off. This allows you to keep your data on long-term basis, while main memory cannot. Given its relatively high capacity compared to main memory at the same price, is much more feasible for use as a mass storage device.

The primary memory, especially RAM, is very fast on modern computers, and since almost directly interfaces with the CPU, which allows very fast transfer between them. Usually it is in the form of memory chips, which store their data electronically and transfer to and from the CPU through a memory bus faster than the computer has been dedicated to this purpose. However, RAM is usually volatile, s that it loses its content when the computer system power is off.

Do not confuse "units or storage devices" to "storage media or devices," because the former are the devices that read or write data stored in the media. The secondary memory is a type of mass storage and permanent (nonvolatile), unlike the RAM that is volatile, but has more memory capacity than main memory, although it is slower. The process of transferring data to a computer equipment is called "reading procedure." The process of transferring data from your computer to the storage is called "procedure of writing."