Whats different with SQL Mobile and SQL Everywhere and SQL Compact Edition, check the following:
SQL Mobile is SQL Everywhere is SQL Compact Edition
So, Microsoft has gone and done it. They’ve released RC1 of their latest reincarnation of SQL Server Mobile/SqlCE. No, it’s not SQL Server Everywhere as we were first told and how it was named (and documented in the CTPs); it’s now (officially) “Microsoft SQL Server 2005 Compact Edition”. And no, they have not agreed on an official acronym but I like SqlCE—kinda like the namespace, so unofficially that’s what I’ll call it until told otherwise. And no, it's not really SQL Server either. SqlCE is an experienced DBMS engine originally created to provide a DBMS for PDAs and (I expect) settop boxes. It's designed to provide an application with a light (small footprint) DBMS that supports a healthy (albeit more limited) SQL syntax and enough datatypes to permit a wide range of data storage options. It can be registered as a merge replication subscriber as well as be protected via full encryption.
Source: William (Bill) Vaughn's Musings: SQL Mobile is SQL Everywhere is SQL Compact Edition
