Question

how cache memory is different from ram and rom

Answer 1

RAM is used for a variety of tasks and is highly versatile, as opposed to ROM and CMOS, which contain crucial — and permanent, in the case of ROM — data related to systems operation, while virtual memory and cache are used to simulate or manipulate RAM during tasks. Virtual memory and cache are designed to enable memory resources for increasingly fast processors.

Answer 2

ROM, or Read Only Memory, cannot be changed and is volatile. (Permanent Storage) . But RAM is non-volatile in nature. ie.Once the power is turned off, the RAM is wiped clear. Hence, the unsaved data gets deleted (Temporary Storage).
Cache gives a CPU fast access to resources by anticipating how much RAM is needed for a task, before allocating that amount for the CPU to use. This means the CPU does not have to draw from the RAM directly, which would slow processes down.