In the currency markets, there is interest paid or earned on positions held overnight (typically any position held at 5pm EST). This is sometimes called "rollover", "swaps", or "TOM/Next", depending on your broker.
How to read the Rollover Calendar:
The number above indicate how many "days" of rollover you can expect to pay or earn on a position held that day at 5pm New York Time (EST). "1" means that day will have typical rollover. To learn more, read our Understanding Foreign Exchange Rollover article.