Updpate from Oct 2024: using vim as a daily editor made me learn these keys in the hard and quick way, so I don't need this note as a reference. Moreover, a lot of these been remapped in my config.
:ls :buffers - list buffers
:buffer <n> - load buffer n to a current window
:edit <file> - create a new buffer with a file
:edit #<n> - edit n-th buffer
:bdelete [n] - delete current or n-th buffer
:[n] + Ctrl+^ - show previous or n-th buffer
ctrl+w s, ctrl+w v - split current window, split vertically
:split [filename], :vsplit [filename] - same as above, optionally loads a file
:q, :qa - close a window, close all windows
:vert help motion.txt - open help in vertical split
ctrl+w _ - maximize currnet window horizontall
ctrl+w | - maximize currnet window vertically
ctrl+w = - make all splits of whe same size
:tabnew [filename] - create a new tab, optionally opening a file
:tabe - new tab with an empty buffer
gt/gT, :tabnext/:tabprev - show next/previous tab
ctrl+w T - move current buffer to a new tab (note the capital "T", so it's ctrl+w shift+t)
_ - go to first char of the line
0 - go to the beginning of the line (to the 0-th position)
f+char - to forward to char, e.g f= jumps right to the closest = in this line
F+char - same as above, but backward
;, , - repeat above jumps in each direction
viw - select the word under cursor ("visual inside word")
vi" - same as above, select everything in ""-s
vi( (same as vi)) - same as above, select everything in ()-s
vip - select the whole paragraph ("visual inside paragraph")
cw - change word (c is for "change", e.g delete and continue in insert mode)
ciw - select the word under cursor ("visual inside word")
yiw, yi" - yank (copy) Word or content in ""s
{, } - move back and forth by paragraph
zA - fold/unfold up to a root level
zM, zR - close / open all folds in a document
^w = - make all split windows of the same size
^w _, ^w | - expand current split vertically/horizontally
gx - open URL under cursor
gf - open file under cursor in current buffer
Ctrl+W f - open file under cursor in a split
m<mark> - mark current position with mark (a single key, e.g: m1, ma, etc).
'<mark> - go to mark (e.g '1 to go mark 1, 'a go to mark a).
ze, zs - horizontall scroll to left/right.
/what, ?that - search forward and backward
n, N - go to next/previous match
/ then ^p, ^n - scroll search history
q/ - open the whole search history into a separate buffer. Go search thru your search history!
:set modified? - check if a buffer was modified
:set modified - mark buffer as modified
:set [no]modifiable - make buffer as [no]-modifiable