Relative provides command which allow you to perform various actions relative to the current file's location allowing you to split, edit, read, etc files in the vicinity of the current file without having to type the full path.

For example, say your current working directory is your home directory and you run the following command:

$ vim some/long/path/to/file1.txt

Now say you want to split on file2 which is in that same directory. Normally you would have to type:

:split some/long/path/to/file2.txt

But with the relative plugin you simply type:

:SplitRelative file2.txt

or

:SplitR file2.txt

The same concept applies for edit, tabnew, read, vimgrep, cd/lcd, etc.

Please see the vim help file for full documentation.