What constitutes fast connection speed depends on where you are. Web Analytics World reports the fastest average Internet speed in the world, as of January 2010, is South Korea's 14.6 megabits per second. Internet service providers' minimum speeds hover around 1Mbps, so anything over 10Mbps is considered fast.
Internet service providers express speed in terms of the number of bits you, the user, receive per second. A fairly high-speed connection of 10Mbps allows you to download roughly 10 million bits per second from the Internet. Upload speeds are generally much slower than download speeds.
According to Microsoft, the most common high-speed Internet connection types are cable or fiber optics. Cable connections run on the same copper wires as cable television, while the faster fiber optic lines use strands of glass to transmit data via light signals.
At 18.7Mbps, Berkeley, California, has the fastest average connection speed in the US. However, according to Gizmodo, the country's fastest single connection belongs to Chattanooga, Tennessee, where residents can obtain a 1 Gbps (1 billion bits per second) connection.