Hi Johnmac,
This refers to a degree of responsibility. In Islam, men are responsible for supporting women, most notably on a financial level although they are responsible for protecting women in every sense (see 4:34). In practice, this means that men are obliged to work in order to support their wives (and families) whereas there is no such obligation upon a woman. Of course, if a woman wishes to work then she is free to do so, provided that her duties and responsibilies in the household are already taken care of. Any money that a woman earns is for herself to spend as she wishes (within the boundaries set by Allah), since she is not obliged to provide for her family.
And Allah knows best.
Regards