A server is just a computer that responds to requests from other computers. Here is the chain:

• DNS servers resolve domain names to IP addresses
• Web servers return the HTML, CSS, and JavaScript that form a webpage
• Application servers run the backend logic — logins, database queries, and dynamic content
• Database servers store and retrieve the actual data — your posts, messages, and account details

When you load a social media feed, your request might touch several servers across multiple countries, each handling a different piece, all within a fraction of a second.