What’s the difference between a virus, spyware, adware & malware?

 Virus Infection

•  - A Virus is a small program that invades your computer and has bad intentions. It
     can replicate and once executed can attach to other programs and can cause different
     levels of harm.

Adware

  

•  - Adware is software with advertising.

Spyware

•   - Spyware spy's for information. Hides in your computer and waits for you to key in 
      username and password to your bank website.  Also searches your computer for   
      credit card information.

Malware

• - Malware is malicious software. In addition malware is a generic term that covers
    all such as adware, spyware, rogue, virus, trojan, worm, rootkit, backdoor and more.

Actually, there is a fine line between adware and spyware, because in many cases adware can report back info as well as advertise without the users' consent and knowledge. You can also add, that banner ads are capable of more than just advertising, malicious users can use them to hide malware and in some cases, doesn't even need users to click on them, it can close and open the website and then direct them to a website where a scan appears and then try to scare users into thinking their computers are infected and pushes rogue software on them.