html The hypertext markup language, commonly referred to as HTML is at the backbone of the internet and World Wide Web. It is the standard markup language used in the creation of webpages and was released in 1993 at the advent of the internet. The format defines the structure and layout of a webpage through markup tags such as header tags and image tags from which a browser can interpret multimedia information for on screen presentation. To view files and webpages saved with the .html filename extension, one needs a compatible web browser that implements the HTML specification. Because the format is open source, several browsers which are mostly free to use can open such files. The World Wide Web consortium actively maintains and updates the html specification.
pdf The .pdf file format extension was developed by Adobe systems in 1993 as a means of presenting documents in a consistent manner across different platforms, hardware, operating systems, and applications. The format was not released as an open source document format until 2008, though minimal proprietary technologies still controlled by Adobe Systems exist in the format. Every .pdf document carries with it the necessary meta information required to properly reconstruct the text, fonts, and graphics used to produce the document. This ensures that documents will be viewed in exactly the same way the author intended regardless of the device used to open the document. From conception to date, Adobe Systems has continued to support the format adding features with every iteration of the standard including hardened algorithms for document encryption and privacy. Today, many freely available readers exist allowing you to open and view .pdf documents and create or convert other file formats such as .jpeg and .doc into .pdf documents.