Internet "History"

Could someone explain the internet "history" for me? When you see something in the history folder, are those websites you've actually accessed... gone into and viewed? Do pop-ups show up in the history or could a virus cause a link to a website show up in the history? I have seen some questionable things showing up in a co-worker's history and want to make sure it's not a virus causing these things to show up. I've run virus scans, adware scans, spyware scans. No viruses have ever shown up. Just want to know if they're actually going in and viewing these websites. Thanks.

 

Ad far as I know those history sites are from either typed urls or navigated pages so that would mean that a popup wouldn't show up. If you have someone viewing sites at your place of business you wish to guard against then you could try putting the sites in the host file so access would be denied..