All items in the game (except for the Modules, which give raw stats) have a special effect, which usually depends on the position of other items. For example: Robot Arm gives +X DMG, where X is the size of the item next to it, or USB Flash Drive, which copies effect of the item next to it. Also, a lot of the effects depend on the type of the items. There are 6 types: Module, Robot Part, Mechanical, Electrical, Scrap and Heart. At the start of the game, you should just swap scrap for some items, and you'll defeat the first enemy!