Like all of the Gemini missions, Gemini 7 was (in part) a stepping-stone to the Moon. One of Gemini 7's goals was to practice an in-orbit rendezvous and docking - that is, approaching and physically connecting with another spacecraft - which was to be a key element of the projected mission to the Moon.
The original plan was for the Gemini 6 (with astronauts Wally Schirra and Thomas Stafford) to dock with Gemini 7 using the separately launched, unmanned Agena target vehicle. But the Agena launch failed, and the Gemini 6 launch was postponed until December 15, so that missions 7 and 6 were launched out of sequence.
In addition to the important rendezvous maneuver, Gemini 7 also provided valuable information on the human body in space:
Nine human life sciences experiments were successfully completed on the G-7 flight, more than on any previous mission. Five of the experiments had been conducted on earlier flights, but all were important for collecting data on physiologic changes taking place over the first long duration flight. The Cardiovascular Conditioning Experiment had been conducted on the G-5 flight for four days; now it was extended to be performed over the entire course of the mission. This experiment investigated the effectiveness of the pneumatic cuff technique in preventing orthostatic intolerance, a condition of low blood pressure after space flight caused by the adaptive body fluid loss in microgravity. The inflatable leg cuffs worn by the pilot pressurized automatically every two minutes out of six in order to stimulate blood movement within the body.
Borman and Lovell are still alive today. They're both 90 years old.