Technology is an industry built around greater and greater efficiency for greater productivity. This relates to just about anything but is most associated with the parts and benefits of a personal computer. Obviously this sector goes back further than the Microsoft revolution but before that there was not a whole lot to invest in. As Microsoft blossomed as a stock from the mid-80s on, more juggernauts like Intel and Orcale joined the fray and with each new development the biggest names changed: AOL, Netscape, Yahoo and finally Google.
The industry will forever be remembered for the "technology bubble" that developed from 1998 to 2000 when the NASDAQ put up 100%+ returns and then went from 5600 to 1800 in less than 2 years. These days it is a diversified group of subindustries that fight for their moment at the top of the heap. Because so much of the focus of the industry is on "new" it will probably always fascinate investors.