It is a new thing.
namespaces
The + directory hierarchy that used to be called packages are now called namespaces, so using an example from the unit testing framework the TestCase class (matlab.unittest.TestCase Class) is in the unittest namespace inside the matlab namespace. But TestCase is not part of any package. See this documentation page for more information about namespaces.
packages
A package, going foward, is as you (and the documentation) said: it's a collection of (hopefully thematically related) software files that also lists what it depends upon (and can be depended upon in turn by other packages.) So you could have a collection of functions related to astronomical calculations in an Astronomy package, but in order to use that you need to have a Physics package installed. So the Astronomy package would declare a dependency on the Physics package, meaning when you install Astronomy it would check if Physics is installed and install it if it is not.
The package could contain functions that are not in any namespace (like sin, plot, etc.), functions inside a namespace included as part of the package (like the Physics package could include a function computeGravitationalForce to compute the force of gravity between two objects given their masses and distance apart), or both.
