This is a new mode (at least for me). So for instance, if you want to add say a
# in front of a bunch of lines, you can do a redo over and over, but the visual mode is a nice way to think about it, you just hit
ctrl-v and then your selection keys like
k select a block of text.
The trick is that when you want to insert something you type
Shift-I that is a capital I and it inserts. I really wanted just to do a lower case
I and then you end the insert mode with an
ESC or a
Of if you want to change a block, then it is
Ctrl-V and then select the block, then
c moves you to change mode and everything you type will change what ever was in the block.