Open Files in Vim Splits
You can open multiple files with Vim in vertical or horizontal splits. To demonstrate, I'll create some test files.
$ touch a.txt b.txt c.txt d.txt e.txt
From the command line, vim -o *.txt
will open these five files in vertical splits. vim -O *.txt
will open them in horizontal splits. This is great for quickly comparing two files side-by-side.