Monty 0.98 is a scripting language that is first compiled into minty byte codes (just like Python). It relies on a unique stack, with specific instructions to manipulate it. monty is an interpreter built specially for the said Monty Bytecodes files.
This is a language that contains specific instructions to manipulate data information (stacks or queues), where each instruction (called opcode) is sent per line. Files which contains Monty byte codes usually have the .m extension.