Plus, chart action for Post Malone, Maggie Rogers & more.

As always, it was a busy week on Billboard's charts. From a new No. 1 on the Billboard Hot 100 to a hugely popular children's song debuting in the tally's top 40 and more, let's recap the most notable action.

Here are 13 things to know about the charts this week.

1. Halsey scores her first No. 1 on the Hot 100 as a lead artist (and second overall), as "Without Me" rises 2-1. Click here for the recap.