million 是百万，1，000，000，数学表示10 的6次方
billion 是一千个million，也就是10亿，1，000，000，000，比million多3个零，数学表示10的9次方
英文解释：
A million is 106, or 1,000,000. A billion is one thousand million, or 1,000,000,000 (109). This is the common usage in English-speaking countries and is called the short scale. Countries in continental Europe and Latin America use the where a billion is a million millions (1012).
The word billion originated from French word bi- (“two”) + -illion; i.e. a million million. It was first coined by Jehan Adam in 1475 as by-million and then rendered as byllion by Nicolas Chuquet in 1484.
Million originated from the Italian milione, from the Latin mille + the augmentative suffix -one.