Because all files contained in it are generated by the kernel at mount time. It contains no permanent files; all changes are lost on system reboot.
The Linux VFS (Virtual File System) may be thought of as a sort of interface between the Linux kernel and the mounted file systems. There can be many different file system types mounted simultaneously and VFS allows the Linux kernel to see and address them all in a similar way. This provides Linux with a great deal of flexibility. [JMH]
The first file system Linux supported was the MINIX file system.
Parallel Virtual File System was created in 2003.
Yes, its called the Page File or the Swap File.
Your question does not make sense. But anyway, virtual memory is basically using harddrive space as fake memory larger than ram. Linux have option to place it on separate partition for efficiency. If you let it use a file, double management of file and virtual memory must be managed.
ext3 is the default file system for Red Hat Enterprise Linux.
hard drive
As 'Linux' is actually the Linux Kernel and a bunch of other tools packaged together as a distro, this will depend on the distro you use. For example, Red Hat Linux uses a file called ks.cfg (known as kickstart) which contains information for it's installer system called Anaconda.
The pros and cons of the Linux file system include the quote saying "On a UNIX system, everything is a file, if something is not a file, it is a process". You can consider this either a pro or a con.
The NTFS file system is supported in Linux by both a kernel module and several userspace programs. It is not supported as a root file system and is not recommended for permanent file storage.
The Linux ext3 file system is the default system in many linux derivatives. It allows for journalling, which the ext2 system did not. It also allows in-situ upgrades without asking for a backup first.
swap file