A headline is the main title or heading of an article, blog post, webpage, or advertisement. It's designed to grab attention, summarizing the content or the main message in a concise, impactful way. An effective headline is key to drawing the reader or viewer in, encouraging them to engage further with the content. Headlines should be captivating, clear, and relevant to the content, often incorporating keywords for SEO purposes. They play a critical role in content marketing and journalism, influencing both the click-through rates and the overall effectiveness of the content.