The presence of a
tour guide and a standard
path to follow through the
exhibit -- whether it be a
historical monument, a
city, a
Windows app, or your
house -- distinguishes the guided tour from its unguided counterpart, where you just
wander around and look at whatever you want for however long you want. Guided tours are available in most major
tourist attractions. I've never liked them myself, but they can be nice in certain places, like a
canyon full of weird plants and features that you couldn't have identified yourself, or
military compounds that you aren't allowed to
explore any other way.
(As a side note, a friend of mine once lost a US$50 bet that our tour guide at Princeton University would have an orange-and-black umbrella with him/her. He based his assumption on the text adventure "Save Princeton." When did they stop carrying those umbrellas? Or did they ever?)