Blog question: Trackback and Pinging

Factual Questions
1

  1. If a blog post asks for a “trackback URL,” is it asking for the third-party website I am referring to, or is it asking for the URL of the blog post that I’m composing?

  2. If I mark “ping URLs” in a blog post, then do I have to bother about trackback URLs at all?

2

And I guess a follow up to No. 1 is that if the URL is the URL of my blog post, then how am I supposed to know what it is before the post goes live?