When people refer to Internet Speed, they are usually referring to the speed of their Internet connection. The speed of an Internet connection is usually categorised by three things,
Ping is measured in milliseconds (ms): the ping of an Internet connection highlights the response time: the speed it takes for your connection to respond to a request. Speed tests can measure your ping by sending an echo request to a remote host and then measuring the response time received by the sender (you). The lower the ping the better: a ping of 100 is reasonable, but a good connection/ping would be something in the region of 20-30. Ping - a good/low ping - is vital in online gaming, where a faster response time - to a users request - will result in better performance.
The download and upload speed of an Internet connection is measured in Mbps - megabit per second. As you have no doubt concluded, the download speed of an Internet connection is the speed it takes to download data, and the upload speed is the time it takes to upload data to the Internet. The download speed of an Internet connection is usually faster than the upload speed of an Internet connection. At present, 2013, the average download speed of an Internet connection in the UK is around about 1.5 Mbps - 3.00 Mbps. The best Internet speed - provided by fibre optic networks - in the UK: can provide a download speed in the region of 50 Mbps. When Internet Service Providers advertise the "Internet Speed" of their service, they usually only provide the download speed of their service.