Parrot is a register based virtual machine being developed by the Perl community. It will be the target for the Perl 6 interpreter. Most other virtual machines like the Java virtual machine are stack based. The developers see it as an advantage of the Parrot machine that it more closely ressembles an actual hardware design and that the vast literature on compiler optimization can be used generating code for the Parrot virtual machine.
The project actually started as an April Fool's joke in which a hypothetical language named Parrot was announced that would unify Python and Perl. Later, the name was adopted be this project whose intent is to do just that. Several tiny languages are developed along with it which target the parrot virtual machine.
The Parrot virtual machine uses Parrot assembly language.