As quoted by Wikipedia:
“The Web platform is a collection of technologies developed as open standards by the World Wide Web Consortium and other standardization bodies such as The Web Hypertext Application Technology Working Group, the Unicode Consortium, the Internet Engineering Task Force, and Ecma International.
The web platform includes technologies such as computer languages and API that help in the making and publishing of a website. It includes CSS, HTML, SVG, MathML, Web storage, Web components, web assembly, XMLHttpRequest, WOFF, HTTP, DOM events, cross-origin resource sharing, etc.