An HDD is a storage which you can find in many desktop computers and notebooks. It is a component, where all your content such as movies, pictures and documents stored. Internal hard drives come in two main sizes. 2.5 inch HDDs will suit notebooks and smaller devices, while 3.5 inch HDD can be found in desktop computers. Consumer HDDs have up to 12TB of storage available. In 2018 this is the most affordable type of storage for your PC.