The UPDATED /180/ Starter Guide (thanks to OP & Germananon)

Stream sources: cricfree, stream2watch; for Yanks, BBC America is streaming it this year.

/180/'s OP: based guy who never fails to open /180/ thread one hour before games start.

Darts Organisations: PDC (only professional players, lots of TV presence, commercially successful, tournaments are big events where spectators get shitfaced) and BDO (old school, manages the grassroots, but usually inferior to PDC in pro segment). For further information on the split: https://en.wikipedia.org/wiki/Split_in_darts

Terms:
Glossary: https://en.wikipedia.org/wiki/Glossary_of_darts
Uncle Bazza: Barry Hearn, Chairman of the PDC, made darts what it is today, always set on squeezing out more money, big Phil Taylor fan
Jobber: A player with no chance of winning a match/progressing very far in a major event or someone who only plays for the prize money and doesn't put any heart or serious effort into his game. Often used as banter.
9-darter: Darts' perfect game, these are very rare.

Main players:
Autism: Nickname for Michael van Gerwen, currently the best player on the planet, nickname derived from his exceptional talent and his slightly autistic antics on the stage. Not really autistic, though.
Philth / Taylel: Nick for Phil Taylor, darts GOAT and world No. 1 from before you were born until not too long ago. The 2018 PDC Worlds is his final professional event before retiring. Widely disliked, mainly because of groping women in 1999 and his utter disgrace of an attitude.
Snackpot/Ferrypot: Nick for Adrian Lewis, great talent, but lazy fatass. Should be winning finals, but prefers eating burgers over practicing and exhibitions on ferries than playing in actual events.
Clown/Clownman: Nick for Peter Wright. Good player, but boring character, which he tries to hide with ridiculous outfits.
Barney: Raymond van Barneveld, former BDO champion who switched to PDC in 2006. Lazy bastard who somehow still has a legion of fans.
Gando: Gary Anderson, 2-times world champion, well known for 1. not giving a shit about smaller tournaments and 2. miscounting.
Superchin: Daryl Gurney, newest first time major winner. Known for his dickishness on stage and general sulking.
Mensur: Mensur Suljovic, unorthodox yet likeable Serbian-born Austrian. Renowned for his favouring of the uncommon D14 as his finishing double and heart-on-sleeve stage antics.
Wolfie (BDO only): Nickname for Martin Adams, BDO hero, true gentleman of the game, never say anything bad about him

Wanna start playing yourself? You'll need eqiupment:
- Board: Winmau Blade 5. Don't buy Unicorn: their boards are notorious for bounceouts!
- Darts (barrels): Not too thin (difficult to handle), not too light, not too expensive. 21-25g is the most common weight range, and don't buy any faggy overpriced signature models. Buy tungsten, not brass.
- Shafts and flights: Buy lots of these. Those need to be replaced a lot. At least 5x3 shafts and 5x3 flights.
- Buy a sharpener. The name is misleading, darts don't need to be sharp, but the sides of the tip need to be roughened up a bit from time to time, so the dart will stick more firmly in the board.
- You need some kind of protection for your wall. Buy one, or make one yourself, thick cardboard will do.
- There are several great scoring apps out there, which can also simulate an opponent at various skill levels. My favourite is n01 - http://www.nakka.com/soft/n01/index_eng.html
- n01 levels/darts per leg: 1-60, 2-40, 3-30, 4-28, 5-26, 6-24, 7-22, 8-20, 9-18, 10-16, 11-14, 12-12. If you beat it at level 12, congrats, you'll be the next world champion.

Practicing:
- Hammering T20 is better than nothing, but it is only a part of the game.
- Practice doubles. Focus on the most popular, like D20 or D16, but also do some around-the-board doubles practice.
- A good and easy practice game is 170: You start at 170 and try to finish with double out. This practices both your doubles skill and your ability to set up finishes.