I've never been divorced, but in some countries it is used to allow a former partner to marry another person. 
same here I have never been divorced or married
Yeah divorcing is legal dissolution of marriage which disolve the bods of matrimony. 
so i guess to divorce it must be legal
It is and people do it for several reasons such as incompatibility, lack of Independence or personality classes. 
I imaging divorce has been around only a short time
Yeah divorce laws have been around for a long time. Most contries require that it be approved by a court. 
the best way to avoid a divorce is not get married :)