Page load time is the amount of time it takes for a web browser to finish loading a website. There is no one cause of page load time, and websites have different page load times depending on the browser used to display them. Browser speed may influence page load time, but your network connection and the website's architecture and planning contribute.
Websites with more advertisements, for example, may take longer to load than those without because your browser must also load the adverts. That's why a browser with built-in ad blocking can load a page faster than one that delivers advertising alongside the content you desire to view or watch.