Just kidding. I of course know that the 1/1/1 is a selection of builds that open up with 1 Barracks, 1 Factory and 1 Starport before making additional Rax or Fact, tech buildings or Command Centers.
Builds revolving around getting this Terran backbone quickly came into fashion after the Beta's initial more aggressive phase, and gained massive popularity due to the build's versatility and security. It should also be noted that any research, besides Siege Mode, is usually delayed unit after expanding to the natural in favor of army size; generally.