I found this great article on the differences between BIOS (basic input/output system) and EFI/UEFI (Unified Extended Firmware Interface), which are the contents of the ROM, which is actually flash memory, non-volatile and writable.
Something to note is that in this context of flash ROM, we could say that ROM means read-only, or not writeable, but from a user perspective rather than a hardware limitation. Updating the (ROM) BIOS/UEFI is a process handled by special applications (BIOS updaters or flashers) that check and update it, or may even be an advanced option offered by the UEFI/BIOS itself.
Althogh the concept of RAM (Random Access Memory), the primary storage keeping instructions and data to be used by the processor, is not tough to grasp, the difference between static and dynamic RAM is a bit tougher. Watch this great video explaining below. Credits go to H3Vtux.
You may also want to watch TechQuickie's "Different Kinds of Memory as Fast As Possible":
And finally, this nice quizlet cards may help you revise the topic of Computer Organisation.
