Anti-virus software is used to prevent, detect and remove computer threats (like the ones mentioned above).
Since viruses can come from many sources, like the Internet or a USB flash drive, the Anti-virus program
has to continuously monitor your computer while you work. When a threat (like say... a virus) is detected
it removes it from your computer. Anti-viruses need to be continuously updated to be able to identify all
the new viruses that are created every minute.
Follow this link to download Avast for free:
Download Avast Anti-Virus
A firewall is software that protects your computer from harmful attacks (like the ones mentioned above)
that try to access your computer through a network (like the Internet). Firewalls works by looking at
all incoming "signals" that your computer may receive. If the firewall finds anyone of those "signals"
suspicious, it will not allow it through to your computer. It can be seen as a barrier between you
and the outside world that protects your computer from any harm. It's almost like an overprotected parent.
Follow this link to download ZoneAlarm for free:
Download ZoneAlarm Firewall
Diagram of how the Internet works
As you can see in the diagram above, there is a link between all computers via the Internet.
This means that a hacker can send a virus to your computer through the Internet! Luckily,
there is a firewall between your computer and the Internet which will stop the virus in its
If the virus does manage to get through the firewall, the anti-virus installed on
your computer will delete the virus, keeping your computer healthy!