What Was A 5-Year Mission?

The Iconic opening of Star Trek the Original Series makes reference to the 5 Year mission of the USS Enterprise NCC-1701 to explore strange new worlds and so on. Under the command of Captain Pike, April and Kirk, we learn that the 5 year mission was something of a grand endeavour from Starfleet Command and entailed a lot of work for starships, so what exactly was it?

Chapters
00:00 Standard Operations
01:30 Developments in Technology
03:27 First 5 Year Missions
04:05 Premise
07:55 Mission Statement
08:42 Post Mission

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This Video is for critical purposes with commentary.

Outro Animation made by @icarogabriel17