What is a Vim buffer?
A buffer is a file loaded into memory for editing. All opened files are associated with a buffer.
How do I identify a buffer?
Vim buffers are identified using a name and a number.
The name of the buffer is the name of the file associated with that buffer.
The buffer number is a unique sequential number assigned by Vim.
This buffer number will not change in a single Vim session
The argument list is a subset of the buffer list. If you've just launched Vim, then the buffer list will be relatively empty.
Buffer List ==> files in vim buffers
Args List ==> files open at the dos/linux command line or open from the vim command line using :args (example open all c files in current directory :args *.c)
Here is a more detailed description and useful tips Buffer List v Argument List