Photo essay by Nathan Myhrvold at Edge.org:
Lions are the only truly social cat, living in groups called prides. A pride is a set of females, often but not always sisters, along with their cubs and subadult cubs. There are also one or more males, usually a coalition of two brothers, but sometimes unrelated lions. Lionesses are the backbone of the pride—they stay together for many years. Males tend to come and go—the typical time frame for them dominating a pride is just 3 to 4 years. Upon reaching adulthood female cubs may stay with the pride. Males never do—they disperse and become nomadic, looking for a pride where they can challenge the dominant male and take over.
Male lions really look the part of the “king of beasts”. Their lives are full of violence, exploitation and sex—in other words just like human royalty through much of history. Male lions sleep an average 20 hours per day. The females on the other hand do all of the really hard work—killing the majority of prey, which the males then appropriate for themselves. The main danger males face is fighting off other males that want to take over their pride and territory. This is serious business; most male lions die in such fights. In between territory fights they are bad tempered and terrorize the females in their pride. In short, they have the lifestyle of pimps.
More here.