To make this clear, we need to go back to history. In November 1996, Netscape, the creator of JavaScript, decided to submit JavaScript to the international standardization organization ECMA, hoping that the language would become an international standard. The following year, ECMA released the first version of the standard document 262 (ECMA-262), which set the standard for the browser scripting language and made the language ECMAScript, version 1.0.
The standard was written for the JavaScript language from the beginning, but it’s not called JavaScript for two reasons. Java is a trademark of Sun, and according to the license agreement, only Netscape can legally use the name JavaScript, and JavaScript itself has been registered as a trademark by Netscape. Second, I want to show that the creator of this language is ECMA, not Netscape, so as to ensure the openness and neutrality of this language.
Thus, the relationship between ECMAScript and JavaScript is that the former is a specification of the latter and the latter is an implementation of the former (other ECMAScript dialects also include Jscript and ActionScript). In everyday situations, the two words are interchangeable.