I don’t know the answer to the title, so I’ll answer the body. The answer is “it depends”.
If you’re talking to someone in a technical setting, then servers are the physical machines. The computers themselves, sitting in a room somewhere. Or maybe a virtual server that pretends to be a physical machine, but runs on a real server that sits in a room somewhere. Whereas a website is some location you can put into a web browser and get content that “feels” like it’s all one thing.
The reason this distinction matters is because you can host multiple small websites on a single server. For example there’s no reason a particular machine couldn’t host 10 different lemmy instances, if it’s got enough processing power.
But on the other hand a popular website may have its work spread across multiple servers. Maybe I’ve got a database server, which is a machine that only runs the database. And then maybe I have a few different web servers that actually serve “the webpage”, but I’ve also got a cache server that stores part of the webpage and serves that when it can, etc. Websites like Facebook or Twitter are considered one website but have thousands and thousands of servers.
But if you’re talking to someone in a non-technical setting, yeah they’re basically the same.