Have you read a magazine before?
Of course, that is a stupid question!
Then you have seen that there are title tags and subtitles or headers that mark important ideas. These headers are typically shown using bold or larger fonts so that readers can quickly identify the point of every single paragraph or group of paragraphs of the text. This helps readers know the content of the text without even reading the entire thing.
So why am I babbling about headers on an article that is about Search Engine Optimization (SEO)?
Because search engine spiders are just text readers; they can only (at this time) see text. But they are lazy readers, they like to see things the way we do. They try to identify the subject of an article or a page as quickly as possible and reading as few words as possible.
This is the point where headers are important: They are the KEY PHRASES that tell search engines what your text is about.
Headers are as important as the title tag that is located next to the meta tags before the body of the HTML code, but header tags are located within the body of your HTML code.
If your pages are not Search Engine Optimized (SEO) then there are probably no header tags on them. However, do not worry about that, just look at your HTML and chose the phrases or the lines of text that you want to convert to headers and then put these tags:
your subtitle text or keyphrase
Note: there are no dots preferring the "h1" and "/ h1" in the real html tag, they were used in order for this html page not to code them as header tags.
By using these tags you are telling search engines exactly where to look.
But how can you take advantage of this knowledge?
By putting your keywords or keyphrases in these headers making search engines know the exact value of the content you offer to your readers.