If one website can be coded in such a way that it will update another website without actually accessing another website through a browser In other words, the updates are done behind the scenes.
If you are not got my point then I present my point another way
if website X can be coded in such a way that it will update website Y without actually accessing website Y through a web browser. In other words, the updates are done behind the scenes.
Be honest I not good with programming websites, so I need your help
If both sites are on the same server, then they can both pull data from the same datastore.
If they are on different servers then one site can act as the datastore but it can make its data available via an api and the second site then requests the data via the api. The api enforces the contract between the two ends.
“If you send me a valid request for the blue widget sales for last month, then I will provide you with a stream which includes that number.”
websiteOne/request.php?item=23&period=last-month
How you handle security, caching and like will be crucial, but once sorted you can have a 100 websites running off the same data if you want to.