You are welcome!
Not to frighten you but here are two lengthy explanations and advice by some experienced participants in the discussions. I would bookmark them and refer to them.
See this thread by Klaus1
Viruses, Trojans, Malware - and other aspects of Internet Security
"DON’T PANIC! But be aware that the Internet is riddled with potential threats to the security and well-being of your Mac or iOS device. No computer system is completely immune from possible attack, but Apple’s OS X (being Unix-based) is less vulnerable than most, particularly the latest versions from Lion onwards. The following seeks to offer some guidance on the main security threats and how to avoid them. If you have further questions please post in the forum appropriate to your particular hardware or operating system."
and this one by John Galt
"The purpose of this User Tip is not to serve as instructions for installing malware. Clearly no one wants to do that, but intrusive and annoying adware has emerged as an increasing threat to one's Internet activity."