Anyone who is, or once was, a part of America's geek culture has encountered and purchased at least one pack of a trading card game. Youngsters would flock to any of the local shops to buy as many packs as their petty allowances would allow just to take in that grand new card smell! Yu-Gi-Oh and Pokemon could be considered to be the "Gate Way" trading card game for a lot of kids growing up in the 90s and into the 2000s, but the famous Magic: The Gathering is the series that managed to get people to stay.
In Magic (created in 1993 by Wizards of the Coast), the player takes the role as a powerful mage known as a Planeswalker who use their lists of spells (their decks) in a battle against other Planeswalkers in an attempt to deplete the other persons life to 0 or making the other player run out of cards from their deck, a technique known as milling. You do this by bringing out lands which act as mana, which is used to bring out enchantments, creatures, artifacts, and spells. Each card in the game has a mana cost in the top right corner, which indicates how much land you need to successfully summon that card. Most cards require you to have very specific combination of lands, requiring people to be very specific on the decks they build.
One of the most famous aspects of the game is its inclusion of a "color pie" with the five colors being red, white, green, blue,and black, each carrying an associated playing style with it. Red is the color of passion, chaos, and emotion and is about dealing direct damage (known as burn) to other players or their creatures. White embodies light, law, and holy magic and its play-style is based on supporting ones cards, healing and protecting the player, and by effecting the overall flow of the battle. Green cards are about life, nature, and tradition and is full of cards that boost your mana (ramping) and bringing out beefy creatures and making them even beefier. Blue is knowledge, illusion, and mental magic and effects the game by allowing the player to draw cards, countering opponents, and delaying others actions. The final color, black, focuses on death, ambition, and ruthlessness and the cards revolve around sacrificing your life and cards for effects, and destroying opponents cards to bring them back as your own.
While a very extensive game, with a ton of different abilities, sets, and viable deck combinations, it is kind of expensive and has a learning curve to it. While buying packs is kind of cheap, expect to flip out hundreds of dollars to make decks that are able to stand groups against other decks found at tournaments. It's easy to find a game though in meat space, since almost every card or hobby store will have Magic players who are usually very accepting to new players, and the Internet is always a good place to go if you want to go over the rules and get hints towards deck building. If it's something you've ever been interested in, give it a chance, because you will most likely have a ton of fun with it.