What happens, if the row parameter of the grid is not supplied?

I thought, that in the case, if you put you row parameter empty (e.g. frame.grid(column=0, pady=5)) it will add this frame after the last occupied row. And it did that in my program. But then I decided to read about this in tcl.tk man doc, and there is a sentence that I can't understand: "If this option is not supplied, then the content is arranged on the same row as the previous content specified on this call to grid, or the next row after the highest occupied row if this is the first content". I can't understand, in what case it will put the content on the same row, in what on the different. Maybe someone could rephrase this in a different words, because can't really understand what did they mean

When using tcl, you can use a single call to grid to arrange multiple widgets on the same row. In tkinter, when you call the grid method you can only use it on one widget at a time.

So, in tcl you can do something like the following, which will put .foo on row 1, and then .bar and .baz on row 2 since the row is not specified on the second line.

grid .foo -row 1
grid .bar .baz

In tkinter you can only call grid on one widget at a time, which means that an unspecified row will always be the next unused row.

Put another way, every time you call grid, all widgets in that single call to grid will be on the same row - either the specified row or the next row. In tcl you can pass multiple widgets at once, but in tkinter you can always only specify a single widget.