Google Web Server

According to the latest NetCraft statistics, 4.45% of websites run on Google's web server. Explain to the fool, what kind of web server is this? And how he scored almost 4.5 percent of the total number of sites (or as much as 8.23%, if you take only active sites)?

PS It should probably also be noted that the share of Apache is steadily decreasing, and IIS is increasing, although Apache leads in absolute terms.