President Trump, vacationing in Palm Beach, Fla., was relatively subdued on Twitter this week — at least until Thursday, when he launched a somewhat arcane broadside at the magazine Vanity Fair. The tweet, dense by Trumpian standards, was a bit confounding, given its highly specific references to rumors and tensions within the Manhattan magazine industry, and a minor Twitter kerfuffle involving a 63-second video about Hillary Clinton.

Phew. Let’s break this down.

1. Vanity Fair: Glossy monthly that has long been a thorn in Mr. Trump’s side; its recently retired editor, Graydon Carter, coined the epithet “short-fingered vulgarian” for the president. On at least 20 occasions, Mr. Trump has tweeted that the magazine is struggling, hence “on its last legs.”

2. apologizing for the minor hit: Last Friday, Vanity Fair’s site The Hive posted a video in which staff members suggested New Year’s resolutions for Hillary Clinton, like they did for a number of people — including the president.

The jokes were not kind; Mrs. Clinton was urged, for instance, to take up a new hobby — “volunteer work, knitting, improv comedy, literally anything that’ll keep you from running again.” This did not sit well among Mrs. Clinton’s fans, including the actress Patricia Arquette, who tweeted at Vanity Fair to “STOP TELLING WOMEN” what “THEY SHOULD DO OR CAN DO.” The hashtag #CancelVanityFair trended.