I am currently using ubuntu 14.04(no windows) on my laptop. Is it mandatory for me to install Virtualbox or VMware to use Cloudera QuickStarts Vm on it.
From Cloudera
These 64-bit VMs require a 64-bit host OS and a virtualization product that can support a 64-bit guest OS.
And
Cloudera QuickStart VMs are available as Zip archives in VMware, KVM, and VirtualBox formats
So yes, you need a virtualization product. Also because the file you will download is just an image and it requires a virtualizer that can play it and let you interact with it.