Search Engines use computer programs called robots to crawl websites and collect information to index them. While crawling, robots might encounter errors, such as broken links, duplicate content which can impact crawl and in turn impacting indexing and ranking of web pages. So removing crawl errors and enhancing the crawlability of website, makes it easy for the robots to index and eventually resulting in better ranking.
This infographics shows you the steps that are involved while search engines crawls a website and steps to fix them.
SearchEnabler SEO platform can also be used to keep a check on crawl errors, as it performs weekly crawl audits pointing out critical errors.