Usually the heading will be the title at the top of a group of information that belongs together.  Subheadings can be used to differentiate different topics under the main heading.  Use headings more sparingly and try to use important keywords (words that clients will Google to find you) in your headings.  Headings should describe the content it seperates.
 
The web standard recommends that 'A heading element briefly describes the topic of the section it introduces' so the words used in the heading should summarise what that next paragraph is about, like the headings in this article do. It also means that the order of the headings should make sense if someone is viewing your website.

When you add text to the heading areas (this means putting text in the heading or subheading field of Webpro), you are effectively telling a search engine how important that text is on the page. Search engines will then use this information when rating your site in their search listings. For good SEO practice, you should always include your website’s keywords in your headings, so that the search engine understands that these are the most important words on the page.
 
Remember that your headings also still need to be readable to your users, and they still need to make sense, so don’t fill them with all your keywords. This is called keyword stuffing and Google will penalise you for this.