some VIM key combo

Normal mode

navigate the text, copy/cut/paste, but also roll-back actions, and so on

basic

Esc or Ctrlc exit from any mode back to normal mode
u undo
Ctrlr redo
`` go to previous cursor position
`. go to previous edit position
; repeat last command
. repeat last text-changing command

navigation

h left / j down / k up / l right
example: 4j moves down 4 lines

w / e go to start / end of next word (punctuation separated)
W / E go to start / end of next word (space separated)
b / ge go to start / end of previous word (punctuation separated)
B / gE go to start / end of previous word (space separated)

( / ) go backward / forward by sentences
{ / } go backward / forward by paragraph
% go to next (or matching) brackets / parentheses / braces
0 / $ go to start / end of line
^ go to first non-blank character of line

gg / G go to first / last line of file
example: 3G go to line 3
H / M / L move cursor to the highest / middle / lowest line of the screen
Ctrlb / Ctrlf scroll a full page up / down
Ctrlu / Ctrld scroll a half page up / down
zt / zz / zb scroll the current line to the top / middle / bottom of the screen
zH / zL scroll half screen to left / right

za toggle current code fold
zo / zc open / close current code chunk
zR / zM open / close all code chunks in file

editing

dd delete (cut) entire line
d$ or D delete (cut) from cursor to the end of line
examples: d3w d5j etc.
dit delete (cut) text inside html tag
di' delete (cut) text inside single quotes, idem for "([{`<
dat delete (cut) html tag and text inside
da' delete (cut) single quotes and text inside, idem for "([{`<

same for yank (copy to vim clipboard): examples: yy y$ etc.

x / X delete (cut) character after / before cursor
p / P put (paste) the vim clipboard after / before cursor

"*y copy to the system clipboard
"*p paste from the system clipboard

>> / << increase / decrease indent for line
example: >5j etc.

g~~ toggle upper / lower case for the line
gUU / guu make upper / lower case for the line
example: gUw gU$ etc.

J / gJ join current line with next line with / without a space between

seek / search

f█ seek forwards to the next instance of █
F█ seek backwards to the next instance of █
t█ seek forwards until adjacent to the next instance of █
T█ seek backwards until adjacent to the next instance of █
; / , repeat seek forwards / backwards

/█ search forwards for regex pattern █
?█ search backwards for regex pattern █

Visual mode

select specific text areas and run commands on them

sub-modes: Visual Line (always select full lines), Visual Block (select any rectangular region)

v Visual mode
V Visual Line mode
Ctrlu Visual Block mode
example: 5V select 5 lines

d delete (cut) selection
y yank (copy) selection
p replace selection
> increase indent
< decrease indent
~ toggle upper / lower case
U / u make upper / lower case
J join lines (remove line break, leading and trailing spaces)

Insert mode

modify the text buffer by typing and removing characters

sub-mode: Replace (replace existing text by directly typing over it)

i / a start insert mode before / after cursor
I / A start insert mode at the beginning / end of the line
o / O add blank line below / above current line

r replace one character
R replace many characters (Replace mode)

cc replace entire line
c$ or C replace from cursor to the end of line
examples: c3w c5j etc.
cit replace text inside html tag
ci' replace text inside single quotes, idem for "([{`
cat replace html tag and text inside
ca' replace single quotes and text inside, idem for "([{`

Bksp / Del
Ctrlw delete current word
Ctrlu delete from the cursor to the first non-blank character of the line

CtrlLeft / CtrlRight go to previous / next word
Home / End go to start / end of line
PgUp / PgDn go to previous / next page
CtrlHome / CtrlEnd go to start / end of file

Commandline mode

more advanced way of executing commands

sub-mode: Ex (more advanced)

:w save change
:w file save change to another file
:q quit (fails if changes not saved)
:wq save & quit
:q! quit without save
:wqa save & quit (all files)
:qa! quit (all files) without save

:explore explore file directory
:bd exit explore
:terminal open terminal
:!command run shell command

:s/old/new/g replace for current line
:%s/old/new/g replace for whole file
:helptopic
:setoptions

examples: :set filetype=fortran, :set background=light, etc.

edit with multiple tabs

vim -p file1 file2 etc.

gt / gT go to next / previous tab
example: 2gt

:tabe file open file in new tab
:tabc close current tab
:tabo close all tabs except current tab