How many is a billion?
If you are American, it is undoubtedly 1,000,000,000. This amount is known to traditionally minded British people as `a thousand million', and by some more adventurous ones as a 'milliard', though this word has not made as much headway in English as in some other European languages. A trillion is then 1,000,000,000,000, and so on.
If you are British, on the other hand, a billion may be 1,000,000,000,000 (a million million), following the older convention.
If you are neither British nor American, you can take your pick! (Both systems were invented by the French, but are called 'British' and 'American' for convenience.)
Once the business world and the financial press found themselves discussing `thousand millions' so much, the 'American' system simply became more convenient, despite a certain lack of logical tidiness. (A 'British' trillion is the third power of a million, while the 'American' one is the fourth power of a thousand, and the 'American' system continues out of sync with the arithmetic). It also makes the profits sound bigger! The 'American' system is now standard use in British government publications, and is becoming the norm in many other languages.