Do you know, że… ?
Z cyklu mało znane opcje operacji…
rounding is an operation with tons of options, you can talk about them for an hour. However, most users don't need to go into detail, because it uses the most popular solution.
However, you can compare the two pictures below. The first shows the default solution when two edges are selected.
And the second picture shows the change after enabling the option Rounded corners. Therefore, this option should be turned on, if you want to keep a sharp edge with a smooth transition at the touching edges.