EnterraHost
A content gap is a keyword a competitor ranks for on page one that you have no page for at all. It is the most actionable report in the product when it is populated, and the most confusing when it is empty, so both cases are worth explaining.
How the report is built
Two inputs, and both have to exist. Competitors have to be confirmed, which happens when you add them or accept a suggestion. Then a full analysis has to run, because competitor rankings are a paid lookup and the crawl does not fetch them.
That is why the screen can say two competitors confirmed, zero gaps, and next monthly run beside each one. It is not broken, it is waiting for the data that produces the comparison.
Why the backlink gap is already there
The lower panel works from referring domains rather than rankings, so it populates as soon as a backlink pull has run. It lists sites linking to competitors and not to you, which is a shorter list than it looks, because most of those domains link to thousands of sites and will never link to yours.
Sort it by domain rank and read the top twenty. If a site links to three of your competitors and publishes articles in your subject, that is a real target. If it links to four hundred sites from a directory page, it is noise wearing a metric.
The order to work the list in
First, the terms you nearly have. A gap where you rank at position fifteen but have no page dedicated to the term is a rewrite rather than a new page, and it is much cheaper.
Second, the terms with volume and a weak competitor. A page eight competitor ranking for a 1,000 search term is beatable. A page one competitor for a 20,000 search term is not, this quarter.
Third, the long tail. Twenty small terms that share one page is a better use of an afternoon than one page for a term you cannot win.
What not to do is write a page for every row. A gap report measures what a competitor has, not what your site should have, and a thin page written to fill a row is a page that competes with your own content.
Deciding a gap is not worth taking
Some gaps are deliberate. A competitor may rank for a term you have decided not to serve, or for a product you do not sell. The useful habit is to mark those decisions somewhere, because the same forty rows will be there next month and reading them twice is how a content plan stalls.
How many competitors to track
Two is enough to start. Each competitor adds real cost to every full run, roughly 80 to 140 credits, and ten competitors on a small pool is a bad trade. Pick the two whose pages you would be embarrassed to lose to, and add more when the pool can carry them.