The term "bifurcation" refers to one of the actions of the judge, where they divide the issues in a trial so that one issue gets decided upon before moving on to the next issues. The reason for doing this may be to avoid prejudice, to economize and expedite, or simply for convenience.
Civil cases are often bifurcated (divided) into damages and liability proceedings. Similarly, criminal trials are separated into guilt and sentencing parts; this is particularly seen in capital cases.
Under family law, bifurcation is seen when divorce is dealt with separately from other related issues such as child support, custody, alimony, etc.