Everything is just about the battles.
Pokémon Showdon is an online Pokémon battle simulator where you can battle thousands of other players in a variety of formats from all of the different generations of Pokémon. Whether you want play some standard 6 vs 6 single battles or battle using randomly generated Pokémon, Showdown is definitely worth checking out.
How do I get started?
Using their teambuilder, you can make whatever team of Pokémon you want (as long as their attacks and stat distributions are legal in game). Here you can select a Pokémon’s stats, ability, moves, level, and even gender to suit your team’s needs. Even if you don’t know the first thing about building a team, you can import someone else’s team to help you get started.
If you’re new to the competitive battling scene and need help putting a team together, you can check out Smogon University. There you’ll find guides for building Pokémon teams, guides for different movesets and stat distributions for every single Pokémon, plus forums where you can share your team builds with other players and get loads of feedback.
How do I actually battle people?
Once you have your team ready, you can jump into one of the dozens of different ladders that Pokémon Showdon has to offer. One of my favorites is Random Battle, a gametype that give two players totally random teams of Pokémon with semi-random movesets. Or if you want to prepare for a local tournament you can check out the VGC playlist, the ladder that uses Nintendo’s official rules for their official Pokémon league tournaments.
From there, battle work like they normally do in Pokémon games. Trainers select their moves, switch out Pokémon, and can chat with their opponent too. The game also tracks every turn move made, so if you want to refer to something that happened earlier in the battle you can certainly do so. Showdown also lets you replay you’re battle and share them with anyone you want; one time I lost to a Luvdisc and now I can replay that battle anytime that I want to feel bad about myself!
Whatever brand of battling you’re into, Pokémon Showdown will surely have something for you. Check it out!