A BDSM club is a club or club-like institution where friends and practitioners of BDSM can gather and meet. BDSM clubs came up in the 20th century and exist in many countries today. They often organize two types of meetings: a) munches and b) BDSM parties.
Some BDSM clubs have their own meeting (and playing) places, while others meet in mainstream places (e.g. pubs or restaurants) for munches, and in BDSM institutions (e.g. BDSM studios) for play-parties. Most BDSM clubs have websites nowadays where they can be contacted and more details can be found.
Most BDSM clubs will welcome anyone who's interested in joining them. Most are open-minded to all kinds of fetishes, sexual orientations and pairings. A minority of BDSM clubs are specialized, such as e.g. only for homosexuals, only maledom, only femdom, or only for people who practice specific "schools" within BDSM, e.g. D/s with no switching.
One of the most famous New York S&M clubs, now gone, was The Vault (at 14th Street and 9th Avenue). After Madonna shot parts of her Sex book there, it became a trendy, more mainstream celebrity hangout, attracting the likes of Heather Locklear, Robert Downey Jr., Tommy Lee, and Pam Anderson. The Sex book includes a photo of a topless Madonna in leather cap, pants, and boots flogging a bound woman in a latex outfit.