Which is the best quick way of jotting down the central idea of this excerpt?

In your own made up quick hand like abbreviations for stuff that you can go back and write later

Delegates: representatives who cast votes at a political party's national convention. binding: if a primary or caucus is “binding” that means the delegates won in that contest are legally bound to vote for a particular candidate at the parties national convention.a primary is a preliminary election used to determine a party's nominee for a specific office. the winner of the party's caucus, or primary, wins the party nomination for that state. then the delegates meet at their party's national party convention, which is a formal gathering of all party delegates from all states.