Comprehend this from a big picture perspective: If I have a big storage box the size of the whole room I could divide it into several parts like closets... one, two, three, etc., I could put stuff here in closet one and stuff there in closet three and divide it into smaller pieces or "isolated containers". If I am in my kitchen I will put separate items in separate containers all in one kitchen closet. The core idea is to divide big boxes to create smaller boxes so they don't contaminate each other.
The same concept applies to machines. For example, when you have big giant machines from Sun/Oracle or Cisco or IBM, you can take those and divide them into smaller virtual machines. Then you can put separate applications self-contained in those smaller virtual machines.
This is where the concept of virtualization comes from. Software companies like Amazon, Microsoft, Google, Facebook, Twitter, and even traditional companies like Boeing and Nordstrom, take their large computer systems and partition them into smaller virtual computers. By doing so, companies and organizations can then manage multiple servers and desktops. This helps them save money, energy, time, and enables the business to run effectively and efficiently.
One example that we would use is VirtualBox.
Like most software we use, VirtualBox is Open Source. It is FREE as in freedom. As our society grows more dependent on computers, the software we run is of critical importance to securing the future of a free society. Free software is about having control over the technology we use in our homes, schools and businesses, where computers work for our individual and communal benefit, not for proprietary software companies or governments who might seek to restrict and monitor us.
VirtualBox is useful for the individual developers. Some other examples of virtual software are Xen, VMWare, Hyper-V and KVM which are typically used for larger deployments.
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