The front cab section had collapsed from the cars piled atop the van. The rear section however was empty. Wade had the good fortune of finding the key to the doors and was able to lock it. Inside Wade stored his school-issued OASIS gear, a lawn chair, space heater, exercise cycle (which he adapted to generate electricity) and sundry items. He also sound proofed the walls by covering them with Styrofoam egg cartons and pieces of carpet.
Wade wired an antenna to the top of the pile of cars in order to gain clear wifi access for his OASIS terminal.
In the movie, the hideout serves basically the same purpose though it appears less damaged than described in the novel. Wade has also covered the walls in information related to James Halliday and his attempts to solve Halliday's Easter Egg Hunt. Following his fight with his aunt and her boyfriend, Wade returns to the hideout to visit Halliday's Journals and doesn't come home for the next few days. Wade is in the hideout when IOI prepares to bomb his home and is thus far enough away to survive. Afterwards, Wade returns to the hideout to broadcast a warning to the rest of the High Five only to be abducted to a gunter hideout.