There are two main functionality differences between RAM and flash memory: RAM is volatile and flash memory is non-volatile, and RAM is much faster than flash memory. RAM stands for Random Access Memory.
In a computer, RAM acts as the computer's running memory. It is hooked up directly to the processor and allows the processor to read and write to it. Due to this every time a program or application runs, the processor assigns it a memory location in RAM. Furthermore, RAM is volatile memory. This means that rather than a hard or solid state disk (which save everything), RAM resets each time that it is turned on and off. This is good because it means that users do not have to manually remove every program from memory.
Flash memory was introduced by Toshiba in 1984 and is an electronic way of storing data. In general, this is used as a non-volatile way of storing data (everything is maintained, even when the device is turned off). A common example is a flash drive. However, attempts to use flash memory as a substitute for RAM have not been successful. While flash memory requires less power, it is also much slower than RAM.