For a bit about the language, read `3bcw` as move `b`ackward by `3` words and `c`hange the `w`ord under the cursor.
The general form of `b` is `[count]b` where
[count] An optional number that may precede the command to multiply
or iterate the command. If no number is given, a count of one
is used, unless otherwise noted. Note that in this manual the
[count] is not mentioned in the description of the command,
but only in the explanation. This was done to make the
commands easier to look up. If the 'showcmd' option is on,
the (partially) entered count is shown at the bottom of the
window. You can use to erase the last digit (|N|).
b [count] words backward. |exclusive| motion.
https://vimdoc.sourceforge.net/htmldoc/intro.html#[count]https://vimdoc.sourceforge.net/htmldoc/motion.html#b
For `c` it’s
["x]c{motion} Delete {motion} text [into register x] and start
insert. When 'cpoptions' includes the 'E' flag and
there is no text to delete (e.g., with "cTx" when the
cursor is just after an 'x'), an error occurs and
insert mode does not start (this is Vi compatible).
When 'cpoptions' does not include the 'E' flag, the
"c" command always starts insert mode, even if there
is no text to delete.
{motion} A command that moves the cursor. These are explained in
|motion.txt|. Examples:
w to start of next word
b to begin of current word
4j four lines down
/The to next occurrence of "The"
https://vimdoc.sourceforge.net/htmldoc/change.html#chttps://vimdoc.sourceforge.net/htmldoc/intro.html#{motion}