Pokemon Showdown is a website dedicated to providing a emulator where people can play pokemon competitively to see who can be the best Trainer.
The Cons of Playing Pokemon Competitively
Playing pokemon can be an incredibly fun game but it does have its drawbacks. First it is very difficult to get a game started with another person. The players both have to own a Nintendo DS and the same generation of pokemon game. Second training pokemon takes time, and lots of it. In a typical playthrough it can take somewhere between 70-90 hours just to beat the Elite Four and even longer after that if they wish to collect all the pokemon in that generation. Third after catching all the pokemon a typical person will then begin the process of making a team that they will use competitively. This part may seem simple, but because there are so many different pokemon the number of choices makes it hard for a player to choose only 6 to be in the team. Fourth the player must begin training his pokemon to level 100, worry about IVs, abilities, moves, nature, and items that the pokemon will hold when they go into battle. This by far is the longest and most grueling part of pokemon. Many times players will "IV train" for hours just to level up one pokemon in a certain way. Pokemon Showdown literally takes all the time involved out and lets the player jump directly into playing the game.
Why this app is awesome!
The problem is time, and Pokemon showdown cuts it all away. First pokemon showdown can be played anywhere you have an internet connection. It can be on a laptop, on a desktop, on a smartphone, and tablets. It runs 24/7 and has very little lag spikes even when there are large amounts of people playing it at the same time. Second battling takes no time at all. If you want to battle with random pokemon against a random person who also has random pokemon is one-click. If you want to make your own team that is easy too. There is a tab for team-builder. There you can type the name of the pokemon, edit its moves, IVs, nature and item that it holds. It even comes with optimal recommendations for each pokemon for competitive play. Once your done editing you can go and battle against other people on the website. There is a long list of people to choose from to randomly battle. Finally if you really want to play competitively you can join the league on the website and battle in rated battles to move up and down the ladder.
There is not much competition in other web apps that I know of. There are always the original Gameboy games that people want to play. These are fun but they do have there drawbacks as listed above in the Cons of playing pokemon competitively.
My guess on how this appworks
Pokemon Showdown is a community driven app. Its source code can be downloaded and edited by any person who has a mac. I believe it is then reviewed by the mods and if they like it they will add the new feature into the web app. It still has a few bugs here and there where pokemon moves don't do exactly what the description says, and the game engine does not quite mirror the one found in most pokemon games, but all in all it looks and feels exactly like the one in the actual pokemon games.