When you ask someone to name a couple of GNU/Linux distributions, in most cases, you will hear the names Debian, Red Hat, Ubuntu and then, SuSE Linux which is now a days known as OpenSuSE.
The reason is that apart from it being one of the oldest Linux distributions around, it has made a name as a distribution which is robust, secure and user friendly. Originally SuSE Linux was owned by a German company by the same name. But in January 2004, it was acquired by Novell which continued to further develop and fine tune it and include more SuSE specific features to it. The end result is a distribution which has grown to have its own unique identity. OpenSuSE is a community program sponsored by Novell and is developed in an open model.
One of the foremost reason to consider OpenSuSE Linux as a very popular Linux distribution is the mere fact that in the past couple of months, it has risen from the bottom of the heap to enjoy second place, just below Ubuntu Linux, in the Distrowatch most popular Linux distributions list.