Primary Memory
Primary memory also known as main memory is accessed directly by the computer. It is used to execute program code and store temporary data. It is made up of Random Access Memory (RAM). This is otherwise known as volatile memory, meaning it is liable to change. Software is temporarily stored in main memory, when being processed by the CPU which is known as executing software. A personal computer will typically have between 1-4 Gigabytes of RAM outside the main CPU.
Secondary Memory
Secondary memory also, secondary storage, on the other hand is a non-volatile, external storage. Examples of such are: hard disks, flash memories or magnetic tape. Secondary memory is used to store data and programs that are not currently in use, however will need to be accessed at some point. Personal computers typically have a few hundred gigabytes of secondary memory in the form of a hard disk.