Anti-virus software is a bit like insurance against flooding, you hope it will never be needed but occasionally it will save your butt.
If you never use the internet your computer is unlikely to need virus protection, but who these days doesn’t use the internet ? Whenever you travel to a web site there is a possibility that the site may contain software that is designed in one way or another to extract from your computer useful information.
Viruses are designed to get out of your computer information that someone else can use to profit from. The most obvious example would be something like your password to your internet bank, but there are other more subtle uses of viruses.
Some viruses are designed to use the processing power of your computer while you are on line to do things that are illegal, such as trying to repeatedly attack another website. This is a form of ransom, the bad people tell a big company to pay up or they will crash the company’s webs site by using your computer and thousands of others.
Anti-virus software is designed to sit quietly in the background and watch what your computer is doing and to watch for websites that are trying to install programs on your computer.
Sometimes it is something simple, like a website that wants to send you advertising on the sly, sometime it is something more dangerous.
Just consider what would happen if your computer was made unusable. Do you have copies of all of those irreplaceable photographs and videos of the family ? If a piece of malicious software makes it on to your computer and encrypts everything, what would you have to pay to get it back ?
There are many different software packages out there that will provide protection against infection, read around the literature and install the one that is the best for you, it may be free (open source) or a subscription service but it is essential in this modern connected world.