All of those values have the meaning you define at runtime. Your application code can inspect the values and decide what to do: change skin, spawn an item, play a sound effect, apply damage, etc. They allow you to do something in the middle of an animation, timed where you have the event key. Often just the name of the event is sufficient, these fields are just extra data if you need it.
The only value that is special in the Spine editor is "audio path". For that, if it is a file path that resolves to an audio file under the Audio node, the editor will play that audio file when the event is encountered during playback in the editor. It is still your application code's responsibility to play the sound at runtime.
If the audio playback or visual indicator above the skeleton bothers you in the editor, you can disable those with the visibility dot next to the event. The visibility dot next to the Events node hides the event keys at the bottom of the dopesheet and graph. When hidden, select the event or Events node to see the event timelines.
