Consider a virtual machine as just that, a machine where you install an operating system and software. IE, you boot/install the OS you want in the VM and then install stuff you want to run on that "device". I run Linux on a VM on my work Windows 7 system, and run Windows XP in a VM on my personal Linux workstation at home, as well as Solaris, QNX, DOS, and other operating systems as needed, each in their own virtual machine (computer). The cool thing is that I can run more than one at a time, and with the network interfaces properly configured, I can communicate between them all.
let me rephrase my question. i knw linux originaly comes with it's onw default virtualizing tool, so what i am saying is how can i use the default virtualization while i am using rhel 6 on a vmware. i hope u get what i mean because i already i have kali linux, redhat 6.0 and window xp already running on my macbook as host
Do you mean, how to you run virtualization on a machine that is, itself, virtual? If that's your question, then the answer is that you just run it.
For fun, I one time ran a VMWare Esxi server. Created a Virtual Xen host inside VMWare. Then I created a Windows Server running Hypervisor inside Xen. Then I ran Win7 inside the hypervisor. Then I ran a ubuntu server running in Virtual box on the win 7 machine.... I had too much time on my hands that day.
Another option that is built into the kernel is LXC (LinuX Containers). It's not full virtualization like KVM, but it's nice and lightweight. It's similar to OpenVZ if you have any experience with that. Here's a link: http://wiki.centos.org/HowTos/LXC-on-CentOS6