Article snapshot taken from Wikipedia with creative commons attribution-sharealike license.
Give it a read and then ask your questions in the chat.
We can research this topic together.
A Pseudocolumn is a "column" that yields a value when selected, but which is not an actual column of the table. An example is RowID or SysDate. It is often used in combination with the DUAL table.
References
Loney, Kevin (2002). Oracle9i The Complete Reference. McGraw-Hill Osbourne. p. 1122.
