What do the repimpexp and the ddlsync uitilities really do?

Hi all,

I would like firstable to understand what the repimpexp utility really does. I found some information that this utility exports or imports (depending on the parameters used) a flat file with the .dat suffix. The file contains all repository data. If this only contains the repository data (metadata), the import of this file wouldn't replace the data contained in the target database (database in the environment where the .dat file is being imported?.

What does the ddlsync utility do? would it also replace all data contained in the database tables in the target environment (import process)?

Can someone confirm me this?.