Actually, Caches works on locality of reference.frequently accessed memory stores on cache memory so memory access time will be lesser.

Cache memory and flash memory are quite different.

cache memory is more expensive per MB than DRAM, volatile, and low latency

flash memory is less expensive per MB than DRAM. non-volatile, and high latency

Neither really has much to do with loading programs into memory, unless

you are loading the program from a thumb drive for example.

cache memory is high speed memory used to try to minimize latency in

accessing high latency large capacity DRAM, It uses the fact that many

programs will access memory sequentially, so a DRAM to cache transfer

of an entire cache line at a time (say 32 bytes at a time) to low latency

but expensive cache memory can mean that instead of 8 successive

high latency 4 byte memory accesses, there is one high latency 4 byte

memory access (which causes an entire cache line transfer) followed by

7 low latency cache memory transfers.

In this way, DRAM can appear to have nearly 1/8 the latency it really has.

Flash memory is what is used in SSDs or USB sticks as faster than

rotating storage, but much slower than DRAM.