Here's why you really need an Antivirus and Firewall.
Lot's of us do not have antivirus's, and we think, well if I don't download anything bad I will never get a virus. Well, this isn't really true. When you visit a website, it could be doing many things behind your back, like Google, Bing, and more. Some websites with bad intentions download executable files to a hidden path on your computer, you will not notice it being downloaded and you will not notice it in your files. If you have an antivirus, it could easily automatically take care of this, without requiring you to manually take any action. Although, if you do not have an antivirus, it can be very easily for hackers to install "rootkit" which is used to spy on your activity and control your PC, and even through at your camera. Most Antivirus's also come with a free integrated Firewall System, which blocks any sort of fully web-based attack. Let's say your home internet speed is somewhere around 80MBPS (this is about the average internet speed), a hacker could send 500MBPS, 1GBPS, or more and take your internet offline. This is called a Denial Of Service Attack, or Distributed Denial Of Service Attack if multiple people are attacking the same target. A firewall could help prevent this, and ease up the attack result, but usually it cannot fully block it. Antivirus's and Firewall's are important, even if you are an "expert" with tech, you probably really need an Antivirus and Firewall.
Avira AV is a free Antivirus and can be downloaded by clicking here.