What is Spam?
"Spam: Commercial e-mails, generally advertising products or services available to buy online, sent to a large number of recipients without their consent."
Why does it matter? What can be done?
If you have an email account the chances are that you will get spam. It's the equivalent of having a house address and getting junk mail through the door. Mostly spam does no harm, it's an inconvenience rather than something which damages your PC, although obviously some of the adverts are for products which you may not want to be aware of.
There are software solutions which will filter the spam before it gets to your inbox and some anti-virus packages will also filter spam. The difficulty with this is that it is not always clear what is spam. Anti-virus packages have been known to filter emails from learning platforms for example.