On the first screen, the tool will present a map for you to choose the proper server. Click on the location that is closest to your location geographically. To see the name of a particular location before choosing, hover your mouse over the orange icon. 

After you've chosen a location, the location's server will begin connecting to your computer.

Once connected, the tool will begin testing the firewall on your computer. This test simply checks to see if there's a firewall on your computer.
 

NOTE: If the tool begins to conduct the speed test at this point, there is a conflict between the server and your firewall. Although the test is merely checking for the presence of a firewall on your computer, your firewall will not permit the tool to fully connect to your computer. You may have to disable your firewall in order for all tests to be completed. At the end of the speed test, it will show you the results of the speed test and display "Firewall Found" for the other tests.

Once the firewall test has completed, the tool will test the latency of your computer. Latency refers to any delay or waiting that increases real or perceived response time beyond the response time desired. For example, when downloading something from the Internet, the time your computer displays to let you know how long it will take the download to complete fluctuates. Although a computer's connection speed fluctuates and the downloading time will adjust to the connection speed, when your computer jumps from "5 minutes" to "35 minutes", this is latency. Specific contributors to computer latency include mismatches in data speed between the microprocessor and input/output devices and inadequate data buffers.

After the latency test, the tool will test the packet loss of your computer. Packet loss occurs when a packet doesn't make it to its final destination and back. It can cause a great deal of problems depending on how much of the packet does not go through and how often it occurs. For example, if you've ever tried to download something from the Internet and the download always seemed to fail, and the package was not corrupt, that was packet loss. 

Last but not least, the tool will test the speed of your service. The speed test will show you how fast it will take a package to download to your computer and how long it will take that same package to upload to a server. Once completed, you will see your calculations much like the picture shown below. For the example shown below, read the statistics:

Firewall Check: TCP is the Transmission Control Protocol and UDP is User Datagram Protocol. TCP enables two hosts to establish a connection and exchange streams of data. TCP guarantees delivery of data and also guarantees that packets will be delivered in the same order in which they were sent. UDP is a communications protocol that offers a limited amount of service when messages are exchanged between computers in a network that uses the Internet Protocol (IP). UDP is an alternative to the TCP. Therefore "Open" means that a connection is allowed. "Closed" means that a connection is not allowed.

Latency Test: The latency time is in milliseconds. The smaller the number (close to 0 seconds), the better. It assures that the time your computer calculates for a download to complete is close to real time.

Packet Loss Test: The number of packets sent should equal the number of packets received. If they are not the same number, this means that your computer is not efficient when sending and receiving packets.

Speed Test: The download speed is how many bits of a package can be received per second. The higher the number, the faster the download. The upload speed is how many bits per second a package can be sent from your computer to a server. The smaller the number, the longer the package will take to send to the server.

Please keep in mind, EarthLink consumer-class products are NOT guaranteed speeds and are instead best effort products.