The phrase "taking the Fifth" is quite commonly bandied about in courtroom TV shows and movies. And as you likely know, when someone who is on trial opts to take the Fifth, he or she is invoking his or her right to decline questioning when on trial.
The Fifth refers to the Fifth Amendment of the Constitution of the United States, which states that no one can be compelled to offer testimony against himself or herself. And if you should go to trial, your attorney will probably advise that you take advantage of this right.
One reason for a defendant to avoid testifying is that it is the prosecution's responsibility to present a case that casts the defendant as being guilty beyond a reasonable doubt. There is no reason for a defendant to risk self-incrimination and help the prosecution by answering questions.
And a defendant cannot be forced to testify by anyone. The prosecution, judge, and jury all must respect a defendant's right to avoid testifying. And the jury is not allowed to view a defendant's refusal to testify as an indication of guilt.
It is important that a defendant understands that the Fifth Amendment is an all or nothing proposition, with no middle ground. That is, as long as you plead the Fifth, you do not have to answer any questions. However, if you should answer so much as a single question after taking the stand, you are compelled to answer all subsequent questions as well. You cannot plead the Fifth selectively.
But choosing to exercise your Fifth Amendment rights does not preclude your voice being heard by the judge and jury when you stand trial. A criminal defense attorney can speak on your behalf. The attorney can act as your representative and present evidence that is in your favor while finding holes and inconsistencies in the prosecution's case in an effort to get your charges dismissed or reduced.