Adventurers League is an organized play campaign for Dungeons and Dragons set in the Forgotten Realms. It was formed about the same time as the current and newest edition of the rules, fifth edition. With the simplicity of the newest version of the rules, AL play has a similar philosophy of very easy entry. They've opened up your options to play, you can join games at public locations such as stores, at conventions, or even private locations or online.
Like most organized play programs, there is a set of common rules so that your character made for one group would be portable to every other group that participates in the program. The rules are nearly the same as what you would have made a character with for a home game, just without the options to roll dice for your statistics or your gold. (with the distributed nature of the campaign, there's no way to have someone actually observe your dice rolls, so they use the more egalitarian point buy to ensure similar starting points).
It's also a much more laid back organization for rules for the Dungeon Master (or DM). Just as the players are expected to adhere to a common set of rules, the DMs are also mildly restricted as to what they can do. They can only run the pre-published adventures approved for the program, such as the hardback adventures released by Wizards of the Coast, or the PDFs that are frequently released on the DM's Guild. There's plenty of materials to run, but you occasionally do run into a craving for a home game.
AL is very friendly to the DM's desire for a smoothly running table of smiling faces, though. They have a section labeled "DM Empowerment" where they encourage you to alter encounters based on how well your group has done, adding monsters if your group is looking for a greater challenge, or removing a monster or two, or reducing hit points, or similar adjustments if your party is having a lot of difficulties. You're encouraged to use your judgment, which is refreshing for an organized play program. I'm also particularly fond of the "DM Quests" which reward a DM for doing the necessary job of running the game. (They work a lot like achievement points in a video game), Not only will you get experience points you can apply to your characters, but more enticing, you get little perks that you can pass onto your players. Today I had four players join that had never played before, and I was able to (within the rules) just add healing potions to the game for the newbies. I was also allowed to give a reward to the players that had brought them. (After all, a DM isn't looking for experience -- playing the game gets you experience -- they're typically looking for ways to make their players have a good time!)
My endless blurbs won't do it justice, the easiest way to see the program is to join a table for a session. If you were ever interested and in the Garden City, Michigan area I'd gladly host a table for you, as we run regular groups at the game store Pandemonium, but if you're not in this area and want to learn, drop me a message. Nothing makes me happier than matching folks up with a table somewhere.
More information is available at http://dndadventurersleague.org