Primary Memory is of two types: RAM and ROM.
RAM (Volatile Memory)
It is a volatile memory. It means it does not store data or instructions permanently. When you switch on the computer the data and instructions from the hard disk are stored in RAM.
CPU utilizes this data to perform the required tasks. As soon as you shut down the computer the RAM loses all the data.
ROM (Non-volatile Memory)
It is a non-volatile memory. It means it does not lose its data or programs that are written on it at the time of manufacture. So it is a permanent memory that contains all important data and instructions needed to perform important tasks like the boot process.