I can’t believe I have never heard of this concept before today. Link to the Wikipedia article in English and in Spanish.
Basically, what this means is it depends on what country you are from, and even in some cases such as Canada, what language you speak.  And if reading a historical document, when it was written, as to what actual value is placed on the word “Billion,” “Trillion,” or so forth. This video explains is very concisely.

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Mexico uses the long scale, United States uses the short scale, Canada uses both, depending on if you’re speaking English or French, Britain changed from the long scale to the short scale in 1975, France changed from the short scale to the long scale in 1961. Several other countries changed at some point, so this gets pretty confusing. See the Wikipedia article linked above for the details.

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