​Control unit: decodes instructions and sends signals to control how data moves around the CPU.​

​Cache: fast access memory for frequently used instructions and data.​

​Registers: small fast memory used to help fetch and execute instructions.​

RAM (Random Access Memory): Temporary holds things for programs until you shut the computer down causing the ram to lose all its memory.​ It also allows applications to apply and use textures of things so it gives a clean feel and experience.
Made up of: Circuit boards on which all the hardware components of RAM are soldered.​
On-chip register's function is the configuration of the basic device operation​

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ROM (Read Only Memory): Permanently hold things for the computer for example the BIOS or the OS System or stuff like programs telling your computer how to boot up and allow you to login.​

Flash Memory: An electronic non-volatile computer storage medium that can be electrically erased and reprogrammed. For example: USB's, SD Cards, External Hard Drive, CD,s

Virtual Memory: Appears to exist as main storage although most of it is supported by data held in secondary storage, transfer between the two being made automatically as required.

The term tertiary storage is used to describe backups and archives of large amounts of data.
ROM cannot be used to save files on as it has very low memory
RAM Cannot be used to save files on as it is volatile
Secondary Storage is useful as it can be used on other computers as well allowing files to be kept personally and be accessed on any computer or device that allows it.
There are many types of Secondary Storage for example:
Hard Disks
Flash Memory Cards/SD Cards
CD-R/Disks
SSD (Solid State Drive)
Blu-Ray™
DAT TAPE
Another alternative for storage is Cloud Storage and is a storage based on the internet meaning it can be accessed through the internet when wanted by the user that had saved it there for example you save something on the Cloud at home like a photo or document and then you can go work or school or somewhere else with internet access you can just sign in or open the cloud storage