If the gap is long and recent, you should acknowledge it in your resume or cover letter. Let's say you’ve been working at a non-industry job to pay the bills -- you may want to fill that period on your resume with a relevant side project you’ve been working on and explain your situation in your cover letter. A qualifier like, “I took a year off to ______ and now am ready to get back into entertainment” is welcomed and helpful to any hiring manager. However, if your gap is under four to six months, or it happened years ago, you can wait until the interview to clarify if it comes up.
Oh, and if the gap is because you were laid off and have been sitting on your couch applying to jobs every day for months but aren’t getting any interviews, you may have a different kind of problem, and you should take advantage of our services.