"Files in Microsoft Project can be saved to disk in a number of formats: .MPP (the default); .MPX (a comma delimited file - Microsoft Project 98 only); .XLS (Excel spreadsheet); .MDB (Access database). Some files (usually databases) can contain all project data. Others are normally used to export/import data using maps. A portfolio of projects can also be saved to Project Server.
'SOURCE; microsoft project glossary-projectlearning.net"