What it says on the can.
JRiver audio engine is the built-in audio renderer of MC which interfaces with audio device drivers on a system.
An input plug-in is code to playback a specific file format (such as flac or mp3), input plug-ins are dll format files.
Microsoft® DirectShow® is an architecture for streaming media on the Microsoft Windows® platform. DirectShow provides for high-quality capture and playback of multimedia streams. An example of a DirectShow filter on MC is LAV filters.
FFmpeg is a free and open-source software project consisting of a suite of libraries and programs for handling video, audio, and other multimedia files and streams.
All the above can be used to decode specific audio and video formats as defined in Tools>Options>File Type
The default for file associations in MC is 'Automatic', I strongly recommend you leave it that way.
Terry
