Hard Disc Drive:
Data that is stored on your computer is actually stored on a Hard Disc Drive (HDD) which is connected to the motherboard that flows the data from your HDD throughout your system where required. This is a platform that allows data that you generate using the computer to be stored onto something.
RAM is something that stores information relative to the programs that are currently being ran on your computer. Without RAM you wouldn't be able to run programs on your computer as there is no storage utility to put information like the program code.
Memory types refers to things like USB sticks, external hard drives and perhaps even magnetic tape. This is an external way of storing data from your computer and all have different ways of storing memory. A more modern memory type that can store data in our day and age is the Solid State Drive (SSD), this is faster than a Hard Disc Drive and is often a lot safer as the data is stored and not written to the device like a HDD.