DEF file basically contains the placement information of macros , standard cells, I/O pins and other physical entities.
LEF file is the abstract view of cells. It only gives the idea about PR boundary, pin position and metal layer information of a cell. To get the complete information about the cell, DEF (Design Exchange Format) file is required.
https://web.archive.org/web/20100613115027if_/http://www.eecs.tufts.edu/~jqiu02/doc/lefdef/lefdefref5.6.pdf