So, you've found some mistakes, some things you could have done better, and you've redone your Book.  Now you want to upload it again, right, and overwrite the older book that is there, and you want to know, are your buyers going to receive this updated book automatically, from Amazon?

Typically, the answer is NO.  

1.If you upload an updated book, only new buyers will receive the updated eBook. Existing buyers—including yourself—will not receive updated eBooks or notification of the availability of an updated version.

2.If you want to see the updated file, yourself, you have to email the KDP and ask them to "push" (that's the term to use) the new eBook to your Content and Devices, from which you can then send it to your Kindle of choice.

3.If you want your readers/buyers to receive an updated copy, you have to write to the KDP, explain the changes you made, explain how what you've done creates a significantly improved end-user experience, (not merely "fixed a few typos"), and if they are convinced, they'll send out notices to your buyers that an updated version is available.

a.Be aware that Amazon doesn't send out notices to your existing customers, "just 'cuz."  They won't do it just because you ask, or ask nicely. You have to make a compelling case that the updates have significant value to your customers. For fiction, 99% of the time, you're going to be out of luck. (I mean, let's face it, Susie Reader isn't likely to go back and re-read your romance or mystery, or whatever, because you tweaked it, right?)  Non-fiction and reference materials stand a better chance of Amazon notifying buyers, as there are decent arguments that updated factual data has value to the buyer.