Can somebody explain target bone?

[Pinesal]

So I see videos of target bones and it looks like they do cool things. However, I (think I) copy the video to reproduce it's results but my rigs don't act the same.

Perhaps someone explaining what bone targeting IS, rather than what it can be used for will help me understand.

[Víctor Paredes]

I made a webinar mainly focused in Targets some time ago. Sadly, the audio is not the best (I couldn't get a better mic for that day), but I think it can be useful for you anyway.