LIGO is the most sensitive and complicated gravitational experiment ever built. To detect gravitational waves even from the strongest events in the Universe, LIGO needs to know when the length of its 4-kilometre arms change by a distance 10,000 times smaller than the diameter of a proton! This makes LIGO susceptible to a great deal of instrumental and environmental sources of noise. Of particular concern are transient, poorly modelled artifacts known by the LIGO community as glitches. Though the reason for having two detectors separated by thousands of miles is to isolate the detectors from common sources of noise, glitches happen frequently enough that they often can be coincident in the two detectors and can mimic astrophysical signals. Classifying and characterizing glitches is imperative to target and eliminate these artifacts, paving the way for more astrophysical signals to be detected.
There are a couple dozen types of glitches that we currently know of. Over time, some glitches have come and gone in the detectors as their causes have been identified (such as an Air Compressor glitch, which was in the data from the first observing run but should not be around anymore as data from future observing runs rolls in). Some glitches have remained a mystery and persisted in the detectors (such as Blip glitches). As of now, the Gravity Spy project has more than persisted20 different options for glitch morphologies, which are described in the pages in this Wiki.