First of all, there are two different formats
Although Data Pump Export (expdp) functionality is similar to that of
the original Export utility (exp), they are completely separate
utilities and their files are not compatible.
Does it follow any standard? : The file format is proprietary. I did not find any rogue documentation on the format online...
The dump file set is made up of one or more disk files that contain
table data, database object metadata, and control information. The
files are written in a proprietary, binary format.
Is it optimized?
Answered by a_horse_with_no_name.
Source: https://docs.oracle.com/html/B28319_02/dp_export.htm