A barred spiral galaxy is a spiral galaxy with a central bar-shaped structure made of stars.
Bars are found in around half of all spiral galaxies, and appear to influence the motions of stars, dust and gas. It is believed that bars act a bit like a funnel, by pulling matter into the bulge from the disk. This leads to central bursts of star formation.
Recent studies suggest that bars are more common now than they were in the distant past, suggesting that they are a sign of maturity. Thus galaxies with bars are thought to be more evolved that those without, and are an important stage on the galaxies transition to become an elliptical galaxy.
Observations of our own galaxy, the Milky Way, suggest that we live in a spiral galaxy with a peanut-shaped bar feature.