A. Before I answer your question, Abby, some people might need a refresher. Java is a required part of many popular programs like LibreOffice, some Adobe programs and popular online games.
Most PCs ship with Java installed by default. Since OSX 10.7, Macs have Java automatically disabled for browsers.
Earlier in the year, hackers began finding dangerous security holes in Java. For a few months, it seemed like every time Oracle - the company that develops Java - patched one, another security hole popped up.
That's why I recommended that people disable or even delete Java. Keeping it around gave hackers a window to completely take over your PC or Mac. Sadly, it meant certain useful programs wouldn't work properly, too.