LCP, CLS & FID are the main terms when we discuss website speed.
Those 3 parameters must fit in some standard predefined values then only your website speed rank will appear as a good number.
LCP – when the page’s main content has likely loaded – It must be less than 2.5 Sec. Don’t confuse LCP with First Contentful Paint (FCP) which is when the browser renders the first bit of content from the DOM
CLS – webpage unexpectedly shifts during its life. For example, if a website visitor loaded a page and, while they were reading it, a banner load and the page jumps down It must be less than 0.1 or less
FID – First Input Delay means when the website is ready to access menus, form controls, and other resources like buttons, etc. It must be less than 100ms