linked tables and appending data - loss of data

Hello

if i link data from another source (Access, Excel, OBDC, etc). will that connection delete or overwrite any data I add to that table on my own.

so, to visualize:

I have a front end in Access that I connect to a maintained sales data table in another Access database that has all but a couple of the products. I need to add data into that connected table. If i refresh the connected table, will me data still be there?

Thanks