A divorce is a complete dissolution of the marriage.
An uncontested divorce is a divorce in which both parties have agreed on everything, including custody, child support, debt and asset division, etc. If both parties have not reached a mutual agreement, the divorce is considered contested.
A contested divorce can involve an argument over property, custody, debt, asset division or any other matter related to the dissolution of the marriage. The deciding factor that makes it a contested divorce is that there is an argument over something requiring a compromise or settlement, or perhaps a hearing before the judge.