Project Gemini was a NASA space program that took place in the 1960s, following the Mercury program. Its main goal was to develop the technology and skills needed for future manned missions to the Moon. Gemini missions involved longer flights, spacewalks, and the ability to rendezvous and dock with other spacecraft. The program consisted of 12 missions, with Gemini 3 being the first crewed flight in March 1965. Astronauts like John Young and Gus Grissom played key roles in these missions. The success of Project Gemini laid the groundwork for the later Apollo program, which ultimately achieved the goal of landing humans on the Moon.