Jargon is a special way to use words that are shared only by a certain group of people. They do not mean what the dictionary says they mean. They have different meanings to the people using them than their everyday meaning.
For example, the ordinary words boot, net, and web also have special meanings for users of computers, the Internet, and the World Wide Web. These, and to flame, to ping and many acronyms are part of net jargon.
An acronym means that only some of the letters in the word or phrase are used. Often this is the first letter of each word. Other acronyms found online are simply common shorthand.
Usually, more jargon is created over time.
Jargon can be used by a clique to prevent others from joining or understanding, but it also is often just used because it is shorter.