What is lost & found file?
 

I made a new ext2 partition with some spare drive space. Mostly to try my hand at partitioning :)

when I mount the new partition a file named lost & found is on the partition. That file is only accessible to root and it appears to be empty.

What is it?

http://www.start-linux.com/print.php?id=173

/lost&found
If a file system check discovers any 'loose' file fragments, it puts them in here. Each partition has its own 'lost&found' directory.
If you find files in there, try to move them back to their original location. If you find something like broken symbolic link to file, you have to reinstall the file(s) from the corresponding RPM, since your file system got damaged so badly that the files were mutilated beyond recognition.