SQLite is an open source software library that implements a self-contained (single file), zero-configuration, transactional SQL database engine. SQLite supports multi-user access, but only a single user can update the database at a time. It is largely an "untyped" system and all data is stored as strings. SQLite is widely used in desktop applications and consumer devices including cellphones, PDAs, and MP3 players.
Compared to Oracle
SQLite is similar to Oracle's Berkeley DB database in that all data is stored in a single file. Starting from 11g, Berkeley DB supports SQL access to relational data, similar to SQLite.
Migration to and from Oracle
Data must typically be converted to text and then loaded using each database's native loader utility. For example, use SQL*Loader to load the text files into an Oracle database. If you can make SQLite accessible via ODBC, you should also be able to use Oracle's Heterogeneous Service to connect to it via a DB link.
An open-source library of Oracle-compatible SQLite functions has been written by students from the Kansas State University. Functions for other DBMS products have also been written.
The StepSqlite product from Metatranz LLC is a PL/SQL compiler for SQLite. It supports a subset of PL/SQL and can be used for code migration or parallel development between Oracle and SQLite.