The carry trade is one of the most widely used forms of financial trading, and the premise that underlies it is simple to understand.

Pay a small commission to take your money in a lower-yielding currency and put it into a higher yielding currency to gain more profit from interest.

Many large banks perform a common version of the carry trade called a currency swap. A currency swap is similar to a eurodollar sweep because it is usually done overnight when the financial markets are closed, because as long as time is moving forward then there is still interest being earned. This concept is important for long term traders who need to know about rollovers.