MTG is a trading card gaem which uses a series of cards to beat your opponents series of cards. its kind of fun. there are a lot of cards
Magic is usually played with a deck of 60 cards, with up to 4 copies of each card apart from basic lands. there are several formats you can play
casual - anything goes meight
standard - a rotating format of the current 2/3 blocks - pretty expensive
modern - non rotating made up of blocks from mirrordin onwards - an attempt to make a cheaper format to get into
legacy - non rotating format with a ban-list to take out some of the really broken stuff. very expensive
vintage - non rotating format played with cards made from solid gold
there are other formats but one of note is commander/edh (my favourite)
100 card singleton deck (no duplicates apart from basic land) with one legendary creature chosen as the commander. the cards in the deck must be of the colours of your commander.
there are also limited formats where you all draw your cards from boosters rather than constructing them at home - often a good way to play so you dont get stomped by money (but then you have to make a deck from what you get). oh yeah, and try to go for sealed - that way you just get a bunch of boosters and open them. draft involves opening a pack, picking a card and passing it around. that sounds confusing to me
http://www.wizards.com/magic/magazine/default.aspx<-- wizards columns
http://forums.mtgsalvation.com/ <--- biggest mtg forums, full of babbies but worth picking bits from
http://www.gatheringmagic.com/ <-- daily articales that are usually ok
http://ertaislament.com/ <-- blog of all the premade decks you can buy
www.deckbox.org <-- deckbuilder site that i like to use
http://magiccards.info/ <-- card search website, i find it easier to use than the offical one
http://cockatrice.de/ <-- online client, barebones and requires knowledge of game but free, complete and functional
Innistrad/Dark Ascension/Avacyn Restored - Gothic Horror theme, graveyard matters (flashback), slightly depowered, pretty cool block, Dark Ascension has undying which brings creatures back to the field with a +1/+1 token when they die as long as they dont have a token on them already, Avacyn restored has lots of big angels and demons etc.
Scars Of Mirrodin/Mirrodin Besieged/New Phyrexia - Return to mirrodin artifact block, lots of stronk cards, awesome set imo
Zendikar/Worldwake/Rise of the Eldrazi - really cool block, has landfall/level up and kicker abilities. rise contains huuuuuge creatures which are just ridiculous. Worldwake is so so but rise and zendikar are awesome.
m13 : bit of a mixed bag with some interesting things in it, exhalted is the returning mechanic, no titans, lots of good commander cards/reprints
m12 : last set with titans, some very good cards, some very mediocre cards