Forex swing trading is when you take advantage of the ups and downs in the markets by quickly selling currency that's decreasing in value or quickly buying currency that's going up in value. I know it looks obvious. This is based on a very important principal:
Things that are going up will keep going up, things that are going down will keep going down (more often than not that's)
If a currency is growing in value the next tick will most likely go up. Losing currency will most likely keep going down on the next tick. The way people can take advantage of this is to basically sit at their computer and buy every time a currency goes up a cent or two. Sell whenever it goes down. This is how day traders make their money. Many of them do so very effectively.
The largest concern with this type of trading is that the brokerage fees can add up to a lot of money. Can eat up a lot of your profit especially if you're trading in smaller amounts of money. The key to combat this is to find a brokerage firm that rewards you with lower fees for traders who make more trades every month. This can save you a pile when you're making hundreds of trades a day.
So in conclusion I'd offer a few basic tips. Stick to one currency, one you know. Trade in high amounts so that brokerage fees take up a smaller amount of your profit. Finally don't fall in love with a currency, trade with your brain.