Localhost refers to the local machine you are currently using, typically identified by the IP address 127.0.0.1 for IPv4 or ::1 for IPv6. When an application sends a network request to localhost, it communicates with itself rather than over the internet. Developers use localhost to run servers, test APIs, and debug applications in a local environment before deploying them.
Why it matters
Localhost provides a safe, isolated environment for development, allowing quick testing without affecting production systems. Understanding localhost is essential when setting up local servers, configuring ports, or working with development tools.
Examples
Running a backend server on http://localhost:3000 or accessing a database running locally. Lessons like Your Computer Is Your Development Server explain this concept.