basically it means you are working in some other country.
To be more specific:
An expatriate (in abbreviated form, expat) is a person temporarily or permanently residing in a country and culture other than that of his upbringing or legal residence. The word comes from the Latin ex (out of) and the greek patria (?????? - country), and is sometimes misspelled (either unintentionally or intentionally) as ex-patriot or short x-pat, due to its pronunciation.
The term is often used in the context of Westerners living in non-Western countries, although it is also used to describe Westerners living in other Western countries, such as Australians living in the United Kingdom, or Britons living in Spain.
Expatriate can just as well be used to describe any person living in a country other than where they hold citizenship, but is generally not used for government officials stationed in a foreign country.
One famous group of expatriates was the so-called "Lost Generation," a term referring to American literary notables who lived in Paris from the time period which saw the end of World War I to the beginning of the Great Depression. This group included people such as Ernest Hemingway, F. Scott Fitzgerald, T. S. Eliot, Ezra Pound, and Gertrude Stein.
A nickname in the UK for former expatriates who have returned to Britain is the "When I"s, or "When we"s, as they are accused of starting conversations by saying "When I was in Rhodesia" or "When we were in Singapore". Similarly, they are sometimes even viewed by their fellow citizens as foreigners, particularly their children, whose accents may seem strange to their classmates. The children of expatriates are often considered Third Culture Kids (or TCKs) and later in life consider themselves "Adult Third Culture Kids" (or ATCKs). These children often hold passports from multiple countries, speak several different languages, and have a hard time defining where "home" is.
The difference between an expatriate and an immigrant is that immigrants (for the most part) commit themselves to becoming a part of their country of residence, whereas expatriates are usually only temporarily placed in the host country and most of the time plan on returning to their home country, so they never adopt the culture in the host country. While Europeans or North Americans living in the Middle East and Asia may marry local people and have children, most see no advantage in adopting citizenship of their host countries, usually because they consider their stay only temporary. In countries like Saudi Arabia, expatriates are required to live in segregated compounds - integration into their host country's society is not an option. As a result a lively community of social blogs has evolved that links the different segregated communities.