An Evidentiary Hearing is a hearing where the judge decides
about one part of the case.  This can include
deciding which parent would be awarded custody of the children.

A trial is considered the final hearing except for an appeal
where the judge decides all remaining issues and can grant the final divorce.

The trial and evidentiary hearing, both parties are expected
to have witnesses testify which can just be including the parties and evidence
to support their arguments. 

There can also be something called ‚ÄúRepresentations of Counsel‚ÄĚ which is what happens at a lot of
the temporary motion stages where the judge just looks at the pleadings and hears
what the attorneys would argue and would be the evidence that would be heard at
an evidentiary hearing or trial. The judge then decides based on the Representations
of Counsel. 

In many courts this is necessary given the time constraints
and the caseloads that the courts have. 
It is very important whether it is an Evidentiary Hearing, Trial or Representations
of Counsel to be properly prepared with your attorney.