Time To First Byte (TTFB): The length of time between a client making an HTTP request to when the client receives the first byte of the request’s response.
Response Time: The duration load time from when a client receives the first byte of the response to when the client receives the last byte of the response.
First Contentful Paint (FCP): FCP measures the length of time it takes for the browser to render the first bit of content from the document object model (DOM). This is an important metric because it provides the first piece of feedback to the user on how the page is loading.
Largest Contentful Paint (LCP): LCP is a Google Web Vitals metric, which measures when the largest content element on a page becomes visible.
First Input Delay (FID): FID measures load responsiveness by assessing the time it takes from when a user first interacts with a page to the time when the browser can begin to process responses for that interaction.
Source : Web Performance Monitoring
Pic Credits : Web Vitals