A backlink gap is the difference between the backlinks or referring domains pointing to your website and those pointing to your competitors. For example, if three competing websites have links from a particular industry blog but your website does not, that referring domain represents a potential backlink gap.The goal is not simply to collect as many links as possible. Instead, you should identify relevant, trustworthy, and useful websites that could naturally reference your content.
https://serpspur.com/tool/backlink-gap/