:help :copy
:help :t
:help :move
:help :range
Copy the lines of the given range below the given line.
To be honest, the more complex part of the copy command is the range that can be given. I will give here only simple examples for ranges.
Copy the current line to the end of the file/buffer.
:.copy$
:.co$
:.t$
.
means current line and $
is here the destination which is after the last line, which makes it the new last
line.
Copy the lines 3 til 10 and insert after line 15.
:3,10co15
Copy the lines from 3 before til 5 after the current line to 10 lines after the current line. For relative ranges it can be useful to turn relative line numbers on.
:set relativenumber
:-3,+5co+10
Copy the range from current line til last line to the beginning of the file.
:.,$co0