On every new upload of a data file, Tableau offers two types of connections to work on it. Live and Extract.
By default, Live is set by Tableau for us to use, assuming that we have all the data on our machine or if the data is on some far away server, the connection is live, healthy and working while you are working on it.
Whenever some data is appended in the original file, the changes won’t reflect in your Tableau worksheet till you refresh it. A Live connection is preferred when your data size is moderate and it’s not dynamic in nature.
But let us consider a scenario where you are travelling to attend a meeting with your customers. The original data file is on some remote server and you don’t have an internet connection. In this scenario Extract connection is a better option to choose.
When you don’t have data with you or if data is dynamic in nature. Extract data would take a screenshot of your entire data at the particular point of time which you can use for analysis while you are offline.
The extracted data would be saved in your computer in Tableau format which won’t reflect changes dynamically. You have to refresh the extracted data for that.
When you create a Tableau public account you can set a default setting to “Allow viz data to be downloaded” — this includes the workbook, the crosstab, and the data. If you did not clicked the setting to allow downloads, there’s no way that you can access the underlying data or the visualisation itself.