The operation keys must be followed by a movement key. 
A doubled operation key affects a line.  For example:
   w 	moves forward one word
   dw	deletes one word
   dd	deletes one line
Also, you can specify a count with these actions.  For instance: 
   2w 	moves forward two words
   d2w	deletes 2 words 
   2dd	deletes two lines

* d     delete a range of text
  y     (yank) copy a range of text into the delete buffer
  Y     Yank the current line; same as 'yy'. (use with P or p (put))
  c     (change) delete a range of text and enter insert mode
  <     shift text left (see autoindent, shiftwidth)
  >     shift text right

Note that delete and yank operate identically, except that yank does not
remove the text.