What does it mean when a king or queen abdicate their throne?

A monarch usually rules his or her nation until he or she dies, or in some cases, deposed. Abdication is the act of relinquishing the throne voluntarily. The reasons for abdication vary. For instance, King Edward VIII abdicated in order to marry Wallis Warfield Simpson, an American divorcee. The Dutch Queens are well known for 'retiring' (abdicating) so their daughters can take over.