From Halopedia, the Halo wiki
The Grappleshot is a piece of wrist-mounted UNSC equipment, which fires a grappling hook that can attach to a surface and pull its user towards it, allowing for easier traversal of their environment. John-117 made use of a grappleshot with his MJOLNIR Powered Assault Armor [GEN3], in May 2560.
The Grappleshot is a piece of usable equipment in Halo Infinite, which the player can use to move rapidly towards a location or enemy. It can also be used to retrieve distant items, such as fusion coils or a gravity hammer. After use, the grappleshot has a short cooldown time before it can be used again. It is available in multiplayer as well, but will function slightly differently than in singleplayer, serving as a battlefield pickup similarly as equipment in Halo 3.
While the Grappleshot's first in-game appearance occurred in Halo Infinite, the idea of a grappling hook has been around for many years, with Bungie or 343 Industries trying the mechanic on several prior Halo titles, ultimately shelving it due to the mechanic not working well.
List of appearances