RAM has a lot more flexibility then ROM due to its random structure. Data can be accessed from any part of the memory and also more than one piece of data can be accessed simultaneously. ROM does not allow this flexibility and is mainly used for firmware chip devices. Since it is read-only, ROM is a very safe means of storage due since it is protected from any alteration.
If you are ever unsure of a word, it is always a good idea to look it up in the dictionary or in an encyclopaedia. This will give you a detailed definition and should also provide a few examples to add context. If you do not own a physical dictionary or encyclopaedia, there is a world of knowledge at your fingertips via the Internet. There are many online dictionaries available to use for free such as www.dictionary.com and online encyclopaedias such as Wikipedia. Once you get to the page you simply find the search bar and then type in the word you wish to find more information about.
You should never be afraid to ask questions as you will gain lots of new knowledge if you start questioning more things.