VMWare Server / Player / Workstation is a very powerful tool allowing one to install several virtual operating systems on one computer. This is not all you get, as you have the ability to run all these OS’es simultanously without need to do anything with your real physical computer. On the other hand this allows to separate different tasks on different machines and prevent software incompatibilities and cross-platform issues.
VMWare Player / Workstation: Good for those users who only need another OS on their computer (Windows on a Mac or Linux or viceversa). It’s much simpler to setup and the workstation is a payed version which allows you to exactly determine sharing the resources on your computer (hard-disk, RAM, Processor). While Player only shares these on fair basis.
VMWare Server: As the name says it out, it suits best for servers (e.g. I used this feature to have a Linux OS on a Windows Server 2008 for logging of a process on a Motoman robot).
It’s pretty simple forward as you could easily download the version of VMWare you want, free of charge (VMWare Workstation is not free) from VMWare website and install it easily. Once this is done, then you need to install your desired OS (Linux, Windows, etc). You could do this either by importing the ISO file or by a DVD/CD. This is simplified by a very easy installation wizard.
Tutorial on how to install OS on WMWare Server: TUTORIAL1
Tutorial on how to install OS on WMWare Player: http://software.intel.com/en-us/articles/creating-a-virtual-machine-on-vmware-tutorial/
VMWare server was a little bit confusing in choosing an ISO file for installing the OS after creating the virtual machine. Here you should Edit the CD, choose ISO from a list of peripherals and then give the address of your ISO file. My version did not show me my own disk (while it showed the whole disk in previously mentioned tutorial), so I had to copy the ISO file from where I downloaded it to the VMWare folder (where all VMWare machines files are stored).