RAM stands for Random Access Memory and today it's mainly spread in form of semiconductors and used in computers and other electronica ldevices for randomly data accessing. Random because you can access anything in RAM in same time as other thing with no dependencies at all. They are volatile because they are easily and often changed and the content is lost after the power is turned off.
ROM stands for Read Only Memory and its used for device firmware chips to store data in order they can be protected from modification.