Vagrant is a tool to create and configure lightweight, reproducible, and portable development environments. By default, it uses Oracle's VirtualBox for these virtual environments, but support for other virtualization systems is available. Most questions about Vagrant should be asked on Super User or Stack Overflow.
Vagrant is a platform independent tool written in Ruby, to create and configure lightweight, reproducible, and portable development environments. By default, it uses Oracle’s VirtualBox for these virtual environments, but support for other virtualization systems is available. Lots of information and very good in-depth documentation can be found on the homepage: Vagrant - Virtualized development for the masses.
Footnote:
Please refer to Meta.SF for some background on the recommendation why questions regarding vagrant are likely to get a better reception and possibly more answers on StackOverflow than on ServerFault.