A virtual tour is a tour online that lets you look around a building or a city. If you are disabled and you can't access things very easy you can look around and you can sometimes feel as if you are there. As you are looking around you get information about the place you are looking around in e.g if you are in a museum you get information about an exhibit. The downside to virtual tours are sometimes you can't see properly and it is very pixilated on some sites. Also you can't go into some buildings to look around, Some of the tours are a little bit outdated.
A perk is that if you are planing a holiday you can look around the place you are planning to go to see what it is like there. My favourite tour was the tour of London because you can see the whole city and experience the whole cities life.