Are Backronym and Acronym same? I don't understand the difference between these two terms.
An acronym is a word formed by the initial letters of other words, such as Nato (North Atlantic Treaty Organisation). Note that this is different to an initialism where the initial letters are spelled out, as in BBC for example.
A backronym is where the word comes first, and the initial letters are made to fit the word. An example is Alex the parrot (Wikipedia) who to date is the only non-human to spontaneously use language and throws doubt on the notion that a large brain is a prerequisite for language. The name Alex was subsequently said to be 'Avian Language Experiment", which then became 'Avian Learning Experiment. As this was decided (or at least stated) after naming the bird, it is a backronym.
Another example would be the USA PATRIOT Act, where :
The title of the act is a ten-letter backronym (USA PATRIOT) that stands for Uniting and Strengthening America by Providing Appropriate Tools Required to Intercept and Obstruct Terrorism Act of 2001
A backronym (Backward acronym or blend of back and acronym) is a term for a word which has been turned into an acronym by inventing an expansion, rather than the other way around. An example given by Wikipedia involves a backronym invented by NASA (itself an acronym - a word formed from initial letters of words and pronounced as a word - for the National Aeronautics and Space Administration):
NASA named its ISS treadmill the Combined Operational Load-Bearing External Resistance Treadmill (COLBERT) after Stephen Colbert. The backronym was a lighthearted compromise in recognition of the comedian's ability to sway NASA's online vote for the naming of an ISS module.
The word backronym was the brainchild of Meredith G. Williams, the winner of the November 1983 edition of the Washington Post monthly neologism contest according to WordSpy.
Backronyms are often used for humorous effect as in the example above (COLBERT), but they are also quite commonly used unintentionally. Other backronyms include
ZIP code: "Zone Improvement Plan" (used to speed up mail processing)
DARE - Drug Abuse Resistance Education
MADD _ Mothers Against Drunk Drivers
Microsoft’s Bing: "Because It’s Not Google"
Ford: "Found On Roadside, Dead"
Delta: "Don't Ever Leave The Airport" or "Don't Expect Luggage To Arrive"
Common acronyms include NASA, NATO, laser, radar, modem, ASAP, etc.