In the 1980s and '90s, it was pretty common for the TV networks to roll out retrospective specials to boost ratings during November and February "sweeps" periods, and this is one of the dozens of Star Trek retrospectives produced over the years. William Shatner hosts from a mock-up of the ship's bridge, introducing a myriad of clips from the show/movies, punctuated by cast interviews.
I watched the original show in syndication when I was a kid, but don't consider myself a Trekker - however, there's virtually nothing in this special that I didn't know already. It's light and fluffy, with remembrances of things such as Nichols' encounter with Martin Luther King, a look at how fictional technology was later actualized, clips, clips and more clips. Also of note, Shatner's segments are nauseating to watch on a large HD TV, with a shaky-cam that rivals the ones used in The Blair Witch Project. Clearly there was some sort of technical problem but they inexplicably used the footage anyway.
I recently caught a rerun of this on the 50th anniversary of Star Trek's debut. For what it is, this isn't a bad special at all - but unless you're a die-hard fan who has to have everything, there isn't much here to warrant seeking out a copy.