The Hubble Space Telescope (HST) works by gradually gathering light from distant objects and using it to build up data about the universe. It does not take photographs, nor does it output pictures in any traditional sense. Rather, the light it collects is translated into data that can be transmitted to astronomers who may or may not choose to convert the data into images, depending on their research needs.
The HST orbits Earth above the atmosphere, which gives it a largely unimpeded view of celestial objects. Each orbit allows its aperture to sweep across sections of the sky from which light can be collected. This light trickles in from distant objects very gradually, and most HST images require several orbits to gather enough light to produce meaningful data. The astronomer who requested the observation is required to program the exact sequence of movements that the HST undertakes to view the object being studied.
The HST has six main instruments for gathering light of various frequencies. Early in the telescope's life, only one instrument was used at a time, but it was later decided to leave all six instruments active during each observation. The data from the five unneeded instruments is handled by a special team, while the requested data is transferred to the team that requested the observation. That team then has one year to analyze the data before it is released to the public.