Ruby is a modern, dynamic, post object-oriented/functional programming language. It blends syntax and features from Perl, Lisp, Eiffel, Ada and Smalltalk, with flexible expressions, dynamic but strict typing, mixins and explicit scoping. It's available in different runtimes, on most platforms, and a complete extension ecosystem.
Lua is a versatile and fast, yet lightweight and embeddable scripting language. It combines basic procedural syntax with complex data types, associative dictionaries, and extensible semantics. It is dynamically typed, uses a JIT bytecode and register-based VM with implicit memory management. It's widely used for scripting within applications and games, or as RAD toolkit.