A mecca is a place that attracts people to it. The huge outlet mall near your hometown is a mecca for shoppers and bargain hunters.
When it's capitalized, Mecca is the holiest city for Muslims, the place where Muhammad was born. Observant Muslims believe it's important to make a pilgrimage to Mecca at some point in their lives. Because this city near the Red Sea draws so many visitors every year, the word mecca gradually came to mean "place where people really want to go." So you might describe Las Vegas as a mecca for gamblers and Cirque du Soleil fans. The original Arabic word is Makkah.