The ad in WandaVision episode seven was for an antidepressant called Nexus. The ad is aimed at women and presents the product as a “unique antidepressant that works to anchor you back to your reality or the reality of your choice”, and it comes with some side-effects, such as “feeling your feelings, confronting your truth, seizing your destiny, and possibly more depression”. The name of this drug is no mere coincidence.
In the comics, beings from the Nexus have the ability to affect probability and future events and jump between dimentions. Kang the Conqueror, the villain in Ant-Man 3 is one of the most powerful of these beings. With the inclusion of this as in the show, we get a smooth introduction to the Nexus and its inhabitants.