Ubuntu is a Debian based Linux operating system developed by UK based company called Canonical Ltd.
Ubuntu is a open source operating system and hence absolutely free to download and install for your use.
Ubuntu is actively maintained by the FLOSS community.( Free/Libre Open-Source Software). The first version of Ubuntu was released on October/20/2014 and latest version(15.10) was released on October/22/2015. Ubuntu is the most user friendly operating system in Linux community with both graphical interface and terminal mode.