pastebin is a generic term for posting text (usually programming code) online so that others can see it.

For example, to collaborate with people on the internet to improve or debug code.

Or to post a long segment of code in an online forum; rather than include the code directly in the post, just post the link to the pastebin.

The original and namesake is;

Two others are hastebin and GitHub Gist

A related site/concept is jsfiddle which allows pasting of all 3 of these: HTML, Javascript, CSS, and will actually run them for you. So it’s a sharing and testing platform in one.