Since no one has really bothered to answer the OP seriously, i'll take a shot at it.
Smash Bros. is a collective type of fighting game.
Wikipedia said:
Super Smash Bros. (ニンテンドーオールスター!大乱闘スマッシュブラザーズ, Nintendō Ōrusutā! Dairantō Sumasshu Burazāzu?, lit. "Nintendo All Star! Great Melee Smash Brothers") is a crossover fighting game developed by HAL Laboratory and published by Nintendo for the Nintendo 64. It was released in Japan on January 21, 1999, in North America on April 26, 1999,[1] and in Europe on November 19, 1999. Super Smash Bros. is the first game in the Super Smash Bros. series, and was followed by Super Smash Bros. Melee for the Nintendo GameCube in 2001 and Super Smash Bros. Brawl for the Wii in 2008. Super Smash Bros. was released for the Virtual Console in Japan on January 20, 2009, one day short of a decade after its original release.
Some of Nintendo's best game developers get a chance to have their star character appear in this fighting game due to their successful games and their popularity.
The Smash Bros series is different from other fighting games in that it sports 3D characters combined with 2D platforming. Methods of attacks also differ in that we use buttons [A,B,X,Y,R,L,Z,C-stick] to defend and attack. Its different in that in most fighter games like Mortal Combat, you have to input a chain of prompts in order to excuse a combo. With Smash the player can make up a string of combos based on situations they arrive to while fighting an opponent.
Mindgames, Strategy's, Technique, Style ; all these things are basically broken down to which character you are playing. Each character is vastly different from the next. In terms of weight, specials, aerials, tilts, grabs and smashes they use. While different, some characters like Dedede and Kirby can preform multiple jumps. Where as Mario can only jump twice. These game play mechanics are often a derivative of where the character originates from. Kirby has always been able to do many jumps in the air in his games because thats his method of getting around. In his games some areas are harder to reach then others, which requires Kirby to be able to jump or float up many times in order for him to get a Max Tomato-- a healing item.
Tournaments - Its our way of finding the answer to the age old question; "Who is the top dog amongst us?" As a motivational tool, money is offered to those who are the most successful of climbing the ranks in the brackets. There are also different methods of creating tournament brackets either with Single or Double elimination.
Wikipedia said:
A single-elimination tournament, also called a knockout, cup or sudden death tournament, is a type of elimination tournament where the loser of each match is immediately eliminated from winning the championship or first prize in the event. (However, it does not always mean that the defeated competitor will not participate further in the tournament: in some such tournaments, consolation or "classification" contests are subsequently held among those already defeated to determine the awarding of lesser places, for example, a Third place playoff.)
A example of a Single Elimination Bracket
Source to article
Wikipedia said:
A double-elimination tournament is a type of elimination tournament competition in which a participant ceases to be eligible to win the tournament's championship upon having lost two games or matches. It stands in contrast to a single-elimination tournament, in which only one defeat results in elimination.
A double-elimination tournament is broken into two sets of brackets, the Winners Bracket and Losers Bracket (W and L Brackets for short; also sometimes Upper Bracket and Lower Bracket, respectively). After the first round, the winners proceed into the W Bracket and the losers proceed into the L Bracket. The W Bracket is conducted in the same manner as a single-elimination tournament, except of course that the losers of each round "drop down" into the L Bracket.
As with single-elimination tournaments, most often the number of competitors is equal to a power of 2 (4, 8, 16, etc) so that there are an even number of competitors at every round.
Example of a Double Elimination Bracket
Source to article
Audience - the primary audience Smash is mainly focused on is the 13-23 age group
roughly. From little brothers and sisters, to college students, the game is intended for everyone to relax enjoy either with items on or off. The game can be played in a very fun and relaxed manner, or it can be enjoyed at very fast paced, high levels of play. It depends on the users preference. To accompany the needs of the many, there are different items allotted for use if one choices to use them.
There are also different modes; either with Stocks[Lives], Timed fights, or Coin collecting. Stocked matches can also have timers if one so chooses. But in a competitive environment [tournies], its usually 3 Stocks and a 8 minute timer.
Welp, hope thats enough to get your started OP. Let me know if you want more information.