No, we're not talking about money! We're talking about the timeliness of information in different information sources.
The information in periodicals is often highly current. Newspapers offer the most extreme example of this, where the information they contain reflects what's happening on a daily basis. Other news sources, such as the magazines Time and U.S. News and World Report, offer weekly digests of current events. Scholarly journals are full of articles that reflect the most recent experiments and research on various topics.
Books, on the other hand, may be current when they are written, but become less current even before they are published. So if you need the most current information on a topic, periodical articles are usually a better bet.
Websites can also be highly current, in some cases more current even than newspapers. Many news sites on the web now offer "raw news", that is, news reports straight from wire services with very little editing or none at all. Unfortunately some of what comes out as "raw news" turns out to be "wrong news"!
You won't always need the most current information available. Much valuable scholarship has been done over the years that is still as relevant today as it was when it was written. But if currency matters, you need to know which sources can give you the most up-to-date information.