These are two acronyms used to mean two different things. I'll go over what they are so that you can be more familiar with what RAM and ROM actually mean.
We'll start off with RAM which is "random access memory" when you look at what the letters mean. When you power off your computer, the RAM is not saved, and it basically is used for doing things on the fly. One example of using RAM is to think of it like a blackboard. You can erase and rewrite it over and over again, because it's not permanent.
A RAM chip:
ROM means "read only memory" and is permanently written to the disk until you erase it, meaning that when you power your computer off the data is still there. This basically is the memory that you have with your computer that holds data on it that tells the computer how to boot up. It can keep data saved even when there is no electricity going through the computer, such as when it's shut off.
1 - http://www.differencebetween.com/difference-between-ram-and-rom/
2 - http://www.webopedia.com/Blog/what-is-the-difference-between-ram-and-rom.html