So Google Search Console has told you you have pages with poor LCP. Or you have run Google Lighthouse on a page that complains of a LCP longer than 4 seconds.
LCP, Largest Contentful Paint, is one of the new Core Web Vitals, which include FID (First Input Delay) and CLS (Cumulative Layout Shift). The Core Web Vitals are part of Google’s new ranking factor: Page Experience that will be implemented in 2021.
But which element on your page is the LCP?