The Oracle distribution all the stuff written to disk during the install proccess (assuming we don't create a database during the install). During install we'll copy all the Oracle binaries into our $ORACLE_HOME directory, which according to the OFA is /u01/app/oracle/product/10.1.0/db_1 for Oracle10g. In here you've got all the binaries that you'll need to work with Oracle, create databases, back them up, manage them, etc.
The other set of files created during install is the Oracle Inventory,
found according to the OFA in /u01/app/oracle/oraInventory. The Inventory
is used by the Oracle Universal Installer to record what products
have been installed, where the were installed, and how. The Oracle Inventory
doesn't impact databases in any way and only impacts the installer.
You can see a list of all the products and options you have installed in
the oraInventory/Components directory.