The difference of running sqlite using "sqlite3" and "rails db"

I'd like to know the difference of running sqlite using "sqlite3" and "rails db".

User-Mini-4:commandsapp user$ rails db SQLite version 3.8.5 2014-08-15 22:37:57 Enter ".help" for usage hints. sqlite>

User-Mini-4:commandsapp user$ sqlite3 SQLite version 3.8.5 2014-08-15 22:37:57 Enter ".help" for usage hints. Connected to a transient in-memory database. Use ".open FILENAME" to reopen on a persistent database. sqlite>