The lighter one represents the WWW, a subset of the Internet. The MIDS Internet Average is a high-level summary of performance data measured from hosts all around the world. It provides one baseline against which more specialized Internet performance data might be compared, serving a similar role as the Dow Jones Industrial Average does in the financial world. However, negligible isn't the same as indetectible. There's a smaller spike on both pinglists about 5PM Monday.
Latency is round trip time, or lag there and back again.
It is a direct measure of Internet slowness. Every 15 minutes we make measurement scans of destinations representing many different Internet services, including routers, DNS servers, and servers specializing in mail, WWW, ftp, news, games, and search engines. These scans are made from some of our beacons, each located on a different network and distributed around the world. Both pinglists show a small packet loss increase on Monday. In fact, they both show spikes at noon and 5PM Monday.