Is Ubuntu a Debian Based System ?
Yes. Ubuntu is a Debian based operating system. Debian is an operating system using Linux kernel. Debian is known for its stability and reliability. So, Canonical built Ubuntu as an operating system based on Debian to maintain a stable reliable OS for users, developers and enterprise companies.
Despite being Debian-based, Ubuntu has too many unique and different features implementation which makes it easily distinguishable from Debian itself. I personally prefer Ubuntu as it is feature rich with somewhat unique looking GNOME environment.