Subways and local trains work much the same in Korea as they do in the states, with maps located around the stations and within each subway car.

subway ticket vending maching in South Korea

A card sometimes known as a T-money card is purchased for various amounts and is scanned each time you enter the station. Each scan of the card deducts a small charge. Once you deplete the funds on your card, you can easily add money to it.

Korean T-money subway cards

Each way is a little less than 500 Korean won or about $0.50 USD. Adding 5,000 or 10,000 won is probably best so losing the card will not be a huge setback, while at the same time, you won't have to constantly be adding fundings to use the subway.

Scanner reading T-money subway card in South Korea

T-money Cards can also be used at vending machines for food and drink around the stations!