How can you determine where a webpage is drawing its data from and when?

I am working on adding some functionality and streamlining speed for a website. My first task is to determine where the website is drawing its data from first when loaded: the web or the database. This is the first time I have gone deep into the code of an actual website so I'm a bit lost trying to navigate how I can determine this. Is there an easy way to determine where the website is drawing its data from first? Any tips on how to approach large amounts of code such as this are greatly appreciated!

You can take a look at the API calls done by the website(which in case of chrome is network tab, besides console). Detailed information is given out there about the network calls done including type of call is done.
In your case, I'm assuming there'd be call for either cases. You can analyse precisely about it from 'Network' tab. If its a DB call it'd make a request to one of the API's of the application, otherwise the web.