:g/Hello/d

Will delete every line containing the text "Hello". Important note: This is not the normal mode command d, this is the ex command :d.

You can use the global command to apply normal mode keystrokes instead of ex commands by prepending normal or norm to the command. For example:

:g/Hello/norm dw

Will delete the first word from every line that contains the text "Hello".

The global command also supports visual mode and ranges.

The command

:g/apples/y A

will yank all lines containing the word apples into the a register, which can be pasted with "ap. Any regular expression can be used.

Note the space before the A, and the capitalization of the register letter. If a capital letter is used as the yank register, matches will be appended to that register. If a lowercase letter is used, only the last match will be placed in that register.

a simple yet very useful command:

:g/ending/m$

moves lines containing ending to the end of the buffer.

m means move
$ means end of buffer, while 0 means beginning of buffer.