(covers information from several alternate timelines)
This planet was located in the Kandari sector. This sector was a region of space in the Alpha Quadrant. Its location in the Milky Way Galaxy was depicted on a Federation star chart in 2293. (Star Trek VI: The Undiscovered Country, production art; TNG: "Conspiracy", display graphic)
It was on a par with Berengaria VII, Vulcan, and even perhaps Earth. (TNG: "Conspiracy"; DS9: "In the Cards") In the 24th century, Andor was the location of the Andorian Agricultural Ministry. There was also a Federation embassy on the planet. (DS9: "The Sound of Her Voice")
Some time before 2363, as a junior officer, Lisa Cusak was assigned as an attaché to the Federation embassy on Andor. She met an Andorian civilian who worked at the Andorian Agricultural Ministry. The two ended up dating for 6 years. (DS9: "The Sound of Her Voice")
In 2373, Kai Winn rhetorically asked Captain Benjamin Sisko if the Federation would be willing to sacrifice Andor (among other worlds) to protect Bajor from the Dominion if necessary. (DS9: "In the Cards")
In 2374, one of the suggestions that Worf offered up for his honeymoon with Jadzia was a mountain climbing expedition on Andor. (DS9: "Change of Heart") After Betazed fell during the Dominion War, many believed Andor might next be threatened. (DS9: "In the Pale Moonlight")
In Star Trek: Enterprise's season 4 DVD, writers Judith and Garfield Reeves-Stevens have said they made the Andorian homeworld a satellite of a gas giant to help explain why both names Andor and Andoria have been used interchangeably. Andor was the gas giant and Andoria was the moon.
"The Explored Galaxy"
"The Explored Galaxy" was a map of charted space in the Alpha Quadrant. Andor was located between the Tholian Assembly and Romulus. Both locations were identified in DS9: "The Search, Part II", "Call to Arms" as being located in this quadrant. This star chart was also seen in several Star Trek: The Next Generation and Star Trek: Deep Space Nine episodes set in the 24th century, from the year 2364 to 2370. These were: TNG: "Conspiracy", "The Measure Of A Man", "The Emissary", "The Mind's Eye", "The Game" and DS9: "In the Hands of the Prophets", "Cardassians".
According to Worlds of Star Trek: Deep Space Nine, Volume 1, the difference between Andor and Andoria was the same as the difference between Terra and Earth. Andoria and Earth being the names preferred by the natives.