(covers information from several alternate timelines)
An episode was a single portion of a television series.
In 2152, Trip Tucker remarked that T'Pol's story of Vulcans making unofficial first contact with Humans in 1957, which he summarized as "Two Vulcans stroll into a bar, hustle a few games of pool and walk out with an armload of TV dinners." sounded like an episode of The Twilight Zone. (ENT: "Carbon Creek")