What is `normal! zvzz` in vimscript?

Question

I found here the following command normal! zvzz

But I don't know what it does.

Answer 1

The normal command simulate keyboard input in normal mode. The normal! version ignore the custom mapping that could have been introduced such that its behavior does not depend on special customization or the presence of plugins.

normal! zvzz trigger the following two normal commnands: zv and zz

zv Open the fold to make the cursor line visible.

zz Center the screen on the cursor line.

From the help:

zv      View cursor line: Open just enough folds to make the line in
        which the cursor is located not folded.

z.      Redraw, line [count] at center of window (default
        cursor line).  Put cursor at first non-blank in the
        line.

zz      Like "z.", but leave the cursor in the same column.
        Careful: If caps-lock is on, this command becomes
        "ZZ": write buffer and exit!