One of the most popular distros for good reasons
Ubuntu is one of the most popular flavors of Linux and along with Mint is strongly recommended for Linux newbies, as it's extremely accessible.
New versions of Ubuntu are released every six months, and every other year the developer Canonical releases an LTS (long term support) version of Ubuntu. These guarantee five years of security and general maintenance updates, so you can carry on using your machine without the hassle of running a full upgrade every few months. Standard releases are supported for one year only.
The current LTS version of Ubuntu uses the Gnome 3 desktop environment, which may be less familiar to Windows and macOS users.
There are variations of Ubuntu which employ different environments such as Lubuntu, which uses a minimal desktop environment based on LXDE and a selection of fast, lightweight applications. This places far less strain on system resources than the graphic-intensive Unity.