An Introduction to Competitive Smash Bros
The Ruleset
There are a few differences between competitive Super Smash Bros and the Smash Bros you probably play at parties. One of the biggest differences is the choice in rulset. Competitive players try to reduce all non-player controlled factors in a game. This includes removing all items, changing the rules to stock, playing strictly 1v1s or 2v2s, and reducing the stagelist to no more than 10 stages.
Competitive Resources
If the ruleset changes didn't scare you off quite yet there are hundreds of players posting various Super Smash Bros. related content on the internet. Some of it is designed to help you learn more about what it takes to win more matches, and some of it is made to keep you entertained. A few notable players that make educational videos are: ESAM, BananaBoySSB and Dabuz.
Following the Super Smash Bros. Scene
There a multitude of ways to follow the competitive scene. Every few weeks, or even more frequently during the summer, a Super Smash Bros. major tournament happens. A majority of the world's best Smash players will compete against each other in 1,000+ person tournaments. A great way to find these major tournaments is through the website start.gg.