A headline is the title of a newspaper story. You'll know the headline, because it's printed in the largest font on the front of the paper.
Printed newspapers have headlines, and online journals, magazines, and newspapers also use headlines. A headline is the title of a story in the paper, and it's usually easy to spot by its large, bold letters. Sometimes television and radio news also use the word headline to mean the biggest, most important news stories of the day. The word was originally a printer's term for the title and page number, and by 1890 it meant "newspaper title."