The Hideout is Kyle's headquarters.
After the first mission, Tara brings Kyle to the Hideout. Once there, he is tasked with finding the other members of the group namely, Buck the gunsmith, Roberto the engineer, Yusif the smuggler, and Herman the scientist. Each of these survivors can be found at their respective workbenches (except for Herman, who is in-charge of the generator), and can provide the Hero with various items.
The survivors' workbenches can be upgraded, allowing the Hero the ability to purchase more powerful equipment and weapons. With each upgrade, their workbenches also look more technologically advanced. Every upgrade of the Tech not only upgrades the generator but also upgrades the look of the whole hideout. Therefore, the once primitive shelter on Tech Level 1 turns into a hi-tech facility on Tech Level 9.