"We look for things."
"What were you looking for?"
"Things we need."
"Can you be more specific?"
"Things that make us go. We need help."
"What is the nature of your mission?"
"We look for things."
A collector was an individual who acquired or collected items of value, either as a profession or as a hobby.
While posing as an Akaali who broke into an antique shop, Jonathan Archer explained to Riaan that he and Trip Tucker were collectors, who were at the store picking up an antique. Riaan, who had been watching the shop for weeks, called out their story, stating that "A real collector would've waited until the shop was open. You're not here to pick up any antiques." Later when Archer and Tucker visited the shop during business hours, he explained to the owner, Garos, that "We noticed antiques in the window. My friend here is an amateur collector." (ENT: "Civilization")
Pakleds were noted collectors, mostly by the means of theft. Geordi La Forge noted, in 2365, that "half the systems" on the Mondor were stolen from the "Romulans, Klingons, Jarada, [and] just about anybody they've ever came in contact with." (TNG: "Samaritan Snare")
According to the biographical file for Kivas Fajo, he was a Zibalian trader who belonged to the Stacius Trade Guild, and was "a noted collector of rare and valuable objects including the Rejac Crystal, "The Starry Night" by Van Gogh, the Lawmim Galactopedia, [and] the Moliam Andi tapestries." Later, after Fajo had been arrested for the theft of Data, and placed in the brig aboard the USS Enterprise-D in 2366, he stated, "Our roles are reversed, aren't they, Data? You're the collector now. Me, I'm in a cage." (TNG: "The Most Toys")
Several collectors visited Deep Space 9 in 2369 for an auction of objects from the Gamma Quadrant, put on by Vash and Quark. Those who attended included Kolos, Stol, and Rul the Obscure. According to Quark, "They're honest collectors of antiquities, every one." When Quark established just how honest they were, Vash suggested that "We'd better keep a close eye on them." (DS9: "Q-Less")
During Deep Space 9's so-called "Third Annual Gratitude Festival" in 2371, Quark sold "genuine latinum-plated renewal scroll inscription pens." that were said to be "blessed by Vedek Redab himself shortly before he passed away." He assured potential customers that "they're sure to become collector's items." (DS9: "Fascination")
Later that year, when USS Voyager entered a region of space occupied by the Bothan, Neelix made "subspace contact with some old friends of mine," including "nomads, collectors, much as I used to be." Due to their line of work, Neelix explained that "They're in a position to gather information during their travels. What they've told me [about the Bothan] doesn't sound good." (VOY: "Persistence of Vision")
According to amnesiac Kathryn Janeway, in 2377, she was "a collector." This was observed when her friend Jaffen spied all of the clutter she had managed to collect over the period of three weeks she had lived at her home. Jaffen was especially curious why she collected spent plasma relays, to which she replied, "I like to think of it as a decorative object." (VOY: "Workforce")
A prominent Zibalian collector named Kerner Hauze died in 2381, leaving behind a large collection to be auctioned off per Collector's Guild rules. Guild Chairman Siggi enlisted the help of the USS Cerritos to catalogue Hauze's collection and dispose of any hazardous materials. During the cataloguing process, Siggi attempted to steal Kahless' fornication helmet, triggering the ship's automated defenses. He initially attempted to pin the blame on Ensign D'Vana Tendi, but was caught when the fornication helmet fell out of his vest. He was killed shortly thereafter, when the ship's security system caused Spock Two's skeleton to fall and crush him to death. (LD: "Kayshon, His Eyes Open")