HoloGrids were a form of portable data storage technology developed by the Wookiees of Kashyyyk. In 19 BBY, the archives of Kashyyyk's Claatuvac Guild were downloaded on to miniature encrypted HoloGrids to prevent their capture by the Galactic Empire. The Guild's main data stacks were then wiped and those Wookiees entrusted with the HoloGrids hid them in locations known only to them.
Chewbacca was one Wookiee Guild member entrusted with a HoloGrid. As first mate of the Millennium Falcon, he shared the information on secret hyperspace routes contained within with Han Solo, allowing them to make smuggling runs in record time. Shortly after the Battle of Hoth, Chewbacca presented the HoloGrid to the Rebel Alliance, which used the information on secret routes to great advantage during the Galactic Civil War.