There are lots and lots of different types of malware, but the main three are Viruses, which are copies itself; needs contact to spread. The next one is the Trojan Horse. It seems legit but it just allows "Back Door" access to your computer. The last one is called Spyware. Spyware is basically where someone can get personal information from you. A lot of times this personal information will be bank account information.
What will make your computer safe?
There are many ways to protect your computer from malware. But three simple ones are, Anti-Virus Software, Firewall, and just plain common sense! Anti-Virus Software will sometimes make your computer slow down, and you will be wanting to turn it off. Don't! Just try a different one! Firewalls will have a little box pop up to say "hey do you really want to do this?" it will help limit your settings so you can know who you are really talking to. Common sense, don't do what sill put malware into your computer!!