One often needs to edit more than one file at a time. For example one maybe editing a header file and a source file at the same time. To edit more than one file at a time, invoke VIM using the following command
$ vim file1 file2 ...
Now you can edit the first file and move onto the next file using the command
You can jump back using the command
It may be useful while coding if you could see both the files at the same time and switch between the two. In other words, it would be useful if the screen was split and you could see the header file at the top and the source file at the bottom. VIM has such a command to split the screen. To invoke i, simply say :split
The same file will be displayed in both the windows. Whatever command is invoked, will affect only the window in focus. So one can edit another file in another window by using the command :e file2
After executing that command, you'll find that there are two files visible. One window shows the first file and the other shows the second file. To switch between the files one has to use the keystroke CTRL-W CTRL-W. To learn more about split windows, just run help on it.