Perhaps a blonde housewife answer will do -
the internet = phone a friend, it's not a thing it's a method.
your computer will connect via wonderwebs (cable or satellite) to other computers
all holding different info's.
So yahoo will have some big puters ("servers") holding the data files of customers and running their own messaging programmes etc.
Web hosting service companies keep the web pages on their computers and charge rent,like a lockup at storagesRus,
They allow search engines like google to access them by keyword search
File sharing like Bit torrent / limewire/ emule is where your pc is allowed to access directly certain files off another individual's computer.
Google themselves have an estimated 200,000 to 400,000 servers - the number and location is not made public for security reasons.
However, The Internet is actually just a way of describing the way information can be shared using virtual/electronic means - so there's no real definition of "where" it is, and how many computers it comprises.
Just like all the postal services and couriers delivering actual letters/your shopping between potentially any home, business, or postbox across the globe.
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