What is the "RAM"?
The RAM, or Random Access Memory of the game, may not seem very important at the beginning of the game. The RAM, however, is what you Software requires in order to run. RAM also limits how much Software you can have running at once.
For example; If I have 10 pieces of Software running at the same time, I need a specific amount of RAM to keep that amount of Software running. DDoSing can immensely damage your RAM, stopping and wiping out your running Software.
Also, the higher the level of your Software, the more RAM it will need to consume, and therefore the more RAM you will have to buy.
How do I buy "RAM"?
To buy RAM, you must first navigate to the "Hardware" section on the side-menu. From there, you can click on "Upgrade Server", which in turn brings up a tab displaying the prices of all Hardware available.