Let me answer u in normal terms...looking at ur mail i guess u r new 2 mainframe n also new 2 projects...
usually we have development, maintenance, enhancement and production related projects....
Developement deals with any new application 2 be made from the scratch
Maintenance deals with already existing project in which we make some n etc
changes like removal of dead-code, applying some new coding standards set by the client......etc
Enhancement deals with already existing project, making some additions 2 tat in accordance with the addition in the business r adding some new features 2 it...etc
Production deals with after an appplication is fully ready for impletation we put tat under observation..