i   # INSERT MODE
ESC # NORMAL (NON-EDITING) MODE
:   # commands start with ':'
:w  # save command; if you are in editing mode you have to hit ESC first!!
:q  # quit file, don't save
:q! # exits WITHOUT saving any changes you have made
:wq # save and quit
R   # replace MODE
r   # replace only one character under cursor
q:  # history of commands (from NORMAL MODE!), to reexecute one of them, select and hit enter!
:w new_filename     # saves into new file
:#,#w new_filename  # saves specific lines (#,#) to new file
:#                  # go to specified line number

$        # moves cursor to end of line
A        # same as $, but switches to insert mode
0 (zero) # moves cursor to beginning of line
CTRL-g   # shows at status line filename and the line you are on
SHIFT-G  # brings you to bottom of file, type line number (isn't displayed) then SHIFT-G # brings you to specified line#

:set nowrap # no word wrapping, :set wrap # back to wrapping
:set number # shows line numbers, :set nonumber # back to no-number mode

vim -o *.txt # opens many files at once and displays them with horizontal
             # split, '-O' does vertical split
vim *.txt    # opens many files at once; ':n' switches between files

:wall or :qall # write or quit all open files
:args *.txt    # places all the relevant files in the argument list
:all           # splits all files in the argument list (buffer) horizontally
CTRL-w         # switch between windows
:split         # shows same file in two windows
:split <file-to-open> # opens second file in new window
:vsplit        # splits windows vertically, very useful for tables, ":set scrollbind" let's you scroll all open windows simultaneously
:close         # closes current window
:only          # closes all windows except current one

:set spell # turns on spell checking
:set nospell # turns spell checking off
:! dict <word> # meaning of word
:! wn 'word' -over # synonyms of word

:set filetype=perl # Turns on syntax coloring for a chosen programming language.
:set syntax on # Turns syntax highlighting on
:set syntax off # Turns syntax highlighting off

u      # undo last command
U      # undo all changes on current line
CTRL-R # redo one change which was undone

x   # deletes what is under cursor
dw  # deletes from curser to end of word including the space
de  # deletes from curser to end of word NOT including the space
cw  # deletes rest of word and lets you then insert, hit ESC to continue with NORMAL mode
c$  # deletes rest of line and lets you then insert, hit ESC to continue with with NORMAL mode
d$  # deletes from cursor to the end of the line
dd  # deletes entire line
2dd # deletes next two lines, continues: 3dd, 4dd and so on.

yy # copies line, for copying several lines do 2yy, 3yy and so on
p # pastes clipboard behind cursor

/my_pattern # searches for my_pattern downwards, type n for next match
?my_pattern # seraches for my_pattern upwards, type n for next match
:set ic # switches to ignore case search (case insensitive)
:set hls # switches to highlight search (highlights search hits)

:s/old_pat/new_pat/  # replaces first occurrence in a line
:s/old_pat/new_pat/g  # replaces all occurrence in a line
:s/old_pat/new_pat/gc  # add 'c' to ask for confirmation
:#,#s/old_pat/new_pat/g  # replaces all occurrence between line numbers: #,#
:%s/old_pat/new_pat/g  # replaces all occurrence in file
:%s/\(pattern1\)\(pattern2\)/\1test\2/g  # regular expression to insert, you need here '\' in front of parentheses (<# Perl)
:%s/\(pattern.*\)/\1 my_tag/g  # appends something to line containing pattern (<# .+ from Perl is .* in VIM)
:%s/\(pattern\)\(.*\)/\1/g  # removes everything in lines after pattern
:%s/\(At\dg\d\d\d\d\d\.\d\)\(.*\)/\1\t\2/g  # inserts tabs between At1g12345.1 and Description
:%s/\n/new_pattern/g  # replaces return signs
:%s/pattern/\r/g  # replace pattern with return signs!!
:%s/\(\n\)/\1\1/g  # insert additional return signs
:%s/\(^At\dg\d\d\d\d\d.\d\t.\{-}\t.\{-}\t.\{-}\t.\{-}\t\).\{-}\t/\1/g  # replaces content between 5th and 6th tab (5th column), '{-}' turns off 'greedy' behavior
:#,#s/\( \{-} \|\.\|\n\)/\1/g  # performs simple word count in specified range of text
:%s/\(E\{6,\}\)/<font color="green">\1<\/font>/g  # highlight pattern in html colors, here highlighting of >= 6 occurences of Es
:%s/\([A-Z]\)/\l\1/g  # change uppercase to lowercase, '%s/\([A-Z]\)/\u\1/g' does the opposite
:g/my_pattern/ s/\([A-Z]\)/\l\1/g | copy $  # uses 'global' command to apply replace function only on those lines that match a certain pattern. The 'copy $' command after the pipe '|' prints all matching lines at the end of the file.
:args *.txt | all | argdo %s/\old_pat/new_pat/ge | update  # command 'args' places all relevant files in the argument list (buffer); 'all' displays each file in separate split window; command 'argdo' applies replacement to all files in argument list (buffer); flag 'e' is necessary to avoid stop at error messages for files with no matches; command 'update' saves all changes to files that were updated.