Many computer users understandably consider Memory and Storage to be the same thing when they are not. This article should help you to understand the different roles both play in a computer.
Storage (HDD, SSD or eMMC) stores long term data on your computer, this may be files like photos, music or an office document. Other data saved to storage includes applications and your operating system. This data is retained when the computer is turned off.
Memory (RAM) stores short-term data. When you open a file (e.g. an office document) from Storage this is temporarily held in Memory while the data is used by the Processor (CPU). Any data in Memory that is not saved to Storage is lost when the computer is turned off.
Memory and Storage work together with your system's Processor (CPU) and all 3 contribute to how your computer performs.