First of all, "javascript" is one word; it's usually possible to distinguish from context between the two unrelated programming languages "java" and "javascript", although the ambiguity should be avoided if possible.

Secondly, Node is used for writing server-side programs in Javascript. Although JS originated as a language for scripts that ran within the client web browser, it is also common as a server-side language. "Node" is the name of the most popular engine for writing server programs in javascript, and you might also see mention of "NPM" or its invocation in scripts; this is "Node Package Manager".