The Audio File Param Node provides a way to open an audio file on your device (i.e. through a file picker), and then outputs it using a data output to be used by other Nodes.
On its own, this Node does nothing, it merely provides an audio file for other Nodes to use, such as an Audio File Sampler Node. This Node is mostly useful for creating custom Nodes with a configurable audio file, or setting the audio file to use across multiple Nodes from a single source.
Outputs
Audio File Output
A data output that contains an audio file, usable by other Nodes which expect an audio file in one of their available data inputs (such as the Audio File Sampler Node).