How Do I Code a "Loading Page" Render?

Not sure exactly what to call this, but I have a page I coded. The page has a lot going on, and when you visit the page, the page is white for a few seconds before rendering. Is there a way to remove the white by rendering a simple “Page Loading” animation, which then disappears after the page is fully loaded?

I can create the “Loading Page” animation and/or graphic, but how do you get this to show instead of the white?

I’m sure a delay is used, which I can create. And I have a feeling, the delay is coded into the “onReady” section at the top of the code. Could use some advice.

Thank you.