For full context and Grapple Glove explanation, you can check out Epic Games’ Fortnite blog post.
The blog goes on to note that Grapple Gloves can be found in “Grapple Glove Toolboxes” located at “Grapple Stops” littered around the island, so make sure to grab one to swing around.
Along with the Grapple Glove, Epic Games dropped some patch notes, tweaking some of the guns.
Each successive swing gets faster until the third swing and beyond, when you’ll be at max speed.”