A million is a word for a number. A single million is a 1 with six zeros after it: 1,000,000. Three million and five hundred thousand is written: 3,500,000. The word million is abbreviated as "million". A thousand million is a billion.
In units of measurement, the Greek word "mega" is used for the multiple of a million. It is abbreviated to "M". MB is the abbreviation of megabyte and means "million bytes". The millionth part is called "micro" and is abbreviated to the Greek letter "μ". We read this as "mü". So a micrometre is a millionth of a metre and is spelt "μm".
Today's word million comes from Italian. In Italian, "mille" means thousand. If you add an "-ione" to Italian words, you mean that something is bigger. A million is therefore a larger thousand. In German, the word appeared as early as around 1530.
Thanks to the million, you can also express very high numbers. In Luxembourg, for example, there are more than half a million people. It is about 150 million kilometres from the earth to the sun. One million seconds is the equivalent of more than eleven days. Sometimes you also say "million" when you just want to say "very much".