How do I use the /playsound command?

I am completely unfamiliar with this command, but I want to know how to use it.

Normally all I have to do is type /[example] and then press tab, and a bunch of options will show up. For an example, when I do /particle [tab] then a lot of particle effects will pop up. But it does nothing when I try the /playsound command. Is there something I need to add to a folder or something?

Also, I don't completely understand the rest of the command either. Please help me.

You can use the /playsound command as follows:

  /playsound soundname (@p for closest player @a for all or @r for random player) x y z volume pitch minvolume

The volume, pitch and player are optional

A list of sounds can be found here in the sound event column.