An Oracle Wallet is nothing more than a protected logical container (a single file named ewallet.p12) that is used for the secure external password store.
See the following link for further details:
http://www.idevelopment.info/data/Oracle/DBA_tips/Security/SEC_15.shtml
Note: Starting with Oracle Database 11g Release 2 (11.2.0.2) on Linux, if the wallet is
being created on a database server, it is recommended to store the Oracle Wallet in
Oracle ACFS (i.e., /u02/app/oracle/wallet/) when ACFS is
available. This applies to single instance, RAC one node, multi-node RAC, but not
Exadata X2 configurations. Oracle ACFS is cluster file system on top of ASM and
provides new Security features like excellent wallet protection and separation of
duties. ACFS is not configured for the example described in this guide and
therefore will not be used for the Oracle wallet.