What is an “agunah”?
An agunah (or chained woman) was traditionally a woman whose husband had disappeared in wartime or at sea, for example. Such a woman could not remarry under Jewish law because her husband cannot be proven to be dead -- in the event he is still alive, he and his wife are still married if he didn’t give her a get before disappearing. As a solution to this problem, in the contemporary State of Israel, many men write their wives a conditional get before leaving for military service. This document assures that if the husband is lost in battle, his wife will be free to remarry and go on with her life.
Today, however, many agunot find themselves "chained" by husbands who refuse to give them a get. This refusal to give a get is a common form of spousal abuse, a way to keep power and control over a woman and prevent her from moving on with her life. Often a man abuses his power by refusing to give a get unless his wife agrees to give him custody of their children, money, or something else that he wants.
Being an agunah can create real hardship and sorrow for a woman, her children, and for all her friends and family. As an agunah, she is unable to re-marry and have full control over her own life decisions. For an Orthodox woman, the inability to re-marry and perhaps have children can make her feel as if she has lost her identity, which may be entirely as a wife and mother.