Code:
vi Makefile # set EXTRAVERSION to a value corresponding to `uname -r`
What the line says is that you have to open up the file named 'Makefile' in a text editor and replace the value of EXTRAVERSION in it with the value you get from the 'uname -r' command.
'#' is a comment indicator, so everything before it is a command and everything after it is extra information. 'vi Makefile' is the command to open the file named 'Makefile' in the program 'vi'. vi is a command-line text editor, one that's available on just about every system. It's a bit advanced and confusing for newbies to use so you may want to substitute a different editor instead, such as nano.
Edit after re-reading: Just to be clear, everywhere you see the `uname -r` command in the instructions is a place where your current version number needs to go (the `backticks` tell the shell to run the command enclosed in them, i.e. they're commands within commands). So what it wants you to do is cd into the source directory of the kernel version you're running, modify the makefile to include the version number, copy the boot-config that also has the same version number, then run the rest of the make commands.
