RAM stands for Random Access Memory and is a chip inside your computer (usually a set of two identical chips) that hold data and programs that are currently in use. If your data and programs remained on your hard drive, it would be significantly slower than it is now.
Each of the ‘sticks’ of RAM inside your machine will be of equal size and are a type of solid state media. This means that there are no moving parts in them allowing them to be quicker and generate less heat.
Imagine the RAM is a little bit like your shopping basket when you go shopping. There are hundred of products all over the shelves that you can select from (much like the data on your hard drive), so if you went to the checkout but had to get each item in turn from the shelves it would take ages! Instead, you move around the shop and put the items that are currently needed into your shopping basket (the RAM), then take them to the checkout (the processor) to be dealt with.
And it’s not just data that is stored in the RAM, any program that is currently running must be stored there too. This allows the program to be accessed quickly and provide instructions to the processor. Even the operating system must be loaded into RAM when the computer is started (booted) and then stored back on the hard drive when the computer shuts down – ever wondered why your teacher looks horrified if you try to shut down your machine by holding down the power button? When you push the power button, you send the CPU into a state of panic and it’s main task will be to save the operating system by saving it into the nearest place on the hard drive. This might not be the best place, and it may not always complete the task perfectly.
So why not just keep the operating system on the RAM if it is used all the time? Well, RAM is volatile. This means that when you switch the power off, all of the memory is lost. Imagine that every time you went to sleep everything you had been thinking about that day was forgotten – in order to remember it, you need to keep it somewhere a bit more long term. The secondary storage is the computer’s equivalent of your long term memory allowing it to remember data when you switch the power back on. Secondary storage is non-volatile.