This brief tutorials will show you how to check you are running unity 3d or unit 2d since they look very much alike,also will show you how to switch between unity and unity 2D.
Unity 2D was mainly designed for those computers do not support hardware acceleration
1.Open a terminal by pressing CTL+ALT+T
2.Run below command to check you are running unity or unity 3D
If the output is ubuntu then you are running unity (unity 3D)