SQLite is also a RDBMS but a lightweight one, it doesn't require it's own process, clustering or user management unlike MySQL or others RDBMS. SQLite consist of a single file and a library to make your application interact with it. The typical example is storing bookmarks on a web browser, or minor database in mobile apps.
SQL is the language standard to interact with RDBMS. While it's the same language, it has minor non-standard variations flavors (like Microsoft's Transact-SQL).
NoSQL is a broad term to refer to databases that are less restricted on the database's model associations than a relational one.
SQL is a programming language to manage data and data definition in RDBMS. ("SELECT * FROM users WHERE lastname = 'Smith';")
NoSQL is a term which describes database systems that don't understand SQL and usually work as key-value store. (Examples: Riak, Redis, MongoDB (document-based))
Wham downvoted. Is this information incorrect?