Walt Disney envisioned Epcot as the heart of Walt Disney World, and his brother, Roy, attempted to make that dream a reality. Alas, Roy passed away in 1971, over a decade before the park was finished.
Epcot stands for Experimental Prototype Community of Tomorrow, and was originally conceived by Walt to be a city for people to live, work and play in. Developers decided to remove the "live" element, and instead created Epcot as a permanent World's Fair.
When it opened on Oct. 1, 1982, the park included a World Showcase with pavilions showcasing cultures from around the world and Future World, meant to show off the latest in science and tech. Both remain staples today. (And yes, the "golf ball," aka Spaceship Earth geosphere, has been there from the beginning.)