Time to First Byte (TTFB) is a web performance metric that measures the time it takes for a user's browser to receive the first byte of data from a server after making a request. It is an important indicator of server responsiveness and overall website speed. A lower TTFB means a faster response, which can enhance user experience and improve search engine rankings. TTFB consists of three main components: the time taken to send the request, the time the server takes to process that request, and the time it takes to send the response back to the browser. Optimizing TTFB can involve improving server performance, reducing network latency, and optimizing database queries.