HTML is HyperText Markup Language. It’s a way of creating formatted text using minimal instructions. Almost all existing web pages use HTML to describe how the letters and boxes on the web page should be displayed.

HTTP is a communications protocol. It is an agreed method of communication between a typical web browser and web server to allow the browser to receive a page that the web server is holding on to. The page that the server hands to the browser is usually in HTML format, although this protocol is also used for serving images and other forms of media.

HTML is a language used in making Web sites.

HTTP/ is a protocol used in communicating between servers and clients.

You can look all of this up on the Internet.

HTTP: Hypertext transfer protocol: this is the language that the websites are written in

HTML: HyperText MarkUp Language: same

I really don’t know how to explain them all

HTTP- “hypertext transfer protocol”…a set of formats used to post content to the internet

HTML- “hypertext markup language”…the code/language used to construct & display internet content

Hypertext Transfer Protocol (HTTP) is a communications protocol used to transfer or convey information on the World Wide Web. Its original purpose was to provide a way to publish and retrieve HTML hypertext pages. Development of HTTP was coordinated by the W3C (World Wide Web Consortium) and the IETF (Internet Engineering Task Force), culminating in the publication of a series of RFCs, most notably RFC 2616 (June 1999), which defines HTTP/1.1, the version of HTTP in common use today.

HTTP is a request/response protocol between clients and servers. The client making an HTTP request – such as a web browser, spider, or other end-user tool – is referred to as the user agent. The responding server – which stores or creates resources such as HTML files and images – is called the origin server. In between the user agent and origin server may be several intermediaries, such as proxies, gateways, and tunnels. It is useful to remember that HTTP does not need to use TCP/IP or its supporting layers. Indeed HTTP can be “implemented on top of any other protocol on the Internet, or on other networks. HTTP only presumes a reliable transport; any protocol that provides such guarantees can be used.”

An HTTP client initiates a request by establishing a Transmission Control Protocol (TCP) connection to a particular port on a host (port 80 by default; see List of TCP and UDP port numbers). An HTTP server listening on that port waits for the client to send a request message.

Upon receiving the request, the server sends back a status line, such as “HTTP/1.1 200 OK”, and a message of its own, the body of which is perhaps the requested file, an error message, or some other information.

Resources to be accessed by HTTP are identified using Uniform Resource Identifiers (URIs) (or, more specifically, URLs) using the http: or https URI schemes.

(Note: in other words, when you type in the address bar the URL for Wikipedia–below–you are asking them to send the information to your computer.)

HTML (Hypertext Markup Language)

File extension: .html, .htm

MIME type: text/html

Type code: TEXT

Uniform Type Identifier: public.html

Developed by: World Wide Web Consortium

Type of format: Markup language

Extended to: XHTML

Standard(s): W3C HTML 4.01

W3C HTML 3.2

HTML, short for Hypertext Markup Language, is the predominant markup language for web pages. It provides a means to describe the structure of text-based information in a document — by denoting certain text as headings, paragraphs, lists, and so on — and to supplement that text with interactive forms, embedded images, and other objects. HTML is written in the form of labels (known as tags), surrounded by angle brackets. HTML can also describe, to some degree, the appearance and semantics of a document, and can include embedded scripting language code which can affect the behavior of web browsers and other HTML processors.

HTML is also often used to refer to content of the MIME type text/html or even more broadly as a generic term for HTML whether in its XML-descended form (such as XHTML 1.0 and later) or its form descended directly from SGML (such as HTML 4.01 and earlier).

(Note: see longer, more explanatory article on Wikipedia)

The Portable Document Format (PDF) is the file format created by Adobe Systems in 1993 for document exchange. PDF is used for representing two-dimensional documents in a device-independent and display resolution-independent fixed-layout document format. Each PDF file encapsulates a complete description of a 2-D document (and, with Acrobat 3-D, embedded 3-D documents) that includes the text, fonts, images, and 2-D vector graphics that compose the document.

PDF is an open standard, and is now being prepared for submission as an ISO standard. (Note:longer article with more details is on Wikipedia)