Are all lawsuits heard before a jury?
Some, but not all lawsuits are heard by a jury. The ability to have a jury of your peers decide your case is guaranteed by the Constitution for things like criminal matters. However, for other issues like divorce, bankruptcy and probate, your case will always be heard by a judge.
Lawsuits - Jury Trial vs. Bench Trial
When most people think of a jury trial, they think of a criminal trial, however, this is not the only example of a situation where you may have a lawsuit decided by a jury. A jury may decide a civil case as well, for example personal injury lawsuits for medical malpractice, or intentional torts. Of course, even when a jury trial is available to you, you don't have to take it. It is possible to instead request a "bench trial" which is a trial where a judge hears the case. This is sometimes done when a case hinges on very technically or legally complex concepts that a jury might not understand fully.
In any case, when a jury is given the authority to decide the case, their opinion is treated with great deference. If a case is appealed (i.e. one of the parties questions the decision and a higher court takes a look at it), usually the "findings of fact" made by the jury are left alone and not questioned. The court tends to look only at whether legal mistakes were made, rather than factual findings regarding things like whether a witness was telling the truth, or whether an event happened like the defendant said it did or like the plaintiff said it did.
It is also interesting to note that in some cases, a jury may even have an impact on the law. Through a process called "jury nullification," a jury can refuse to convict someone for something that is technically a crime even if the person is guilty, because the jury believes the law is unfair or that it is being unfairly applied in the trial at hand.
If you are involved in a lawsuit or a criminal trial, you need to consult with a lawyer for help in determining whether it is in your best interests to have a jury trial or not.