MySQL is a fully featured RDBMS. An example would be enterprise system or websites.
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.