Refers to an empty space on a form, document, or screen; also used adjectivally with な to mean 'empty' or 'blank'.
Please fill in your name in the blank space on the application form.
The screen went blank.
Used for a period when one is away from a regular activity, such as work, study, or practice; often implies a break that may cause a decline in skill or knowledge.
If you have a gap in your work history, it's tough to come back.
After a ten-year hiatus, he resumed playing the piano.
She has a five-year gap in her career.
Please leave that field blank.
He made up for lost time by practicing repeatedly.