Scrap is a resource in Duskers and serves as the main currency for the game.
Each ship has a scrap capacity which determines how much scrap you can hold at any given time. This capacity can be seen in the System View under the derelict information panel.
Don't let your scrap capacity fill all the way up. If you have enough scrap (~15 less than maximum), hold on to your extra drones and upgrades. You can scrap them if you start to run low.