What is Isabelle/HOL

Isabelle/HOL is an interactive theorem prover and programming language that is designed to support formal verification of mathematical proofs and software systems. It is based on the Higher-order Logic (HOL) framework, which provides a powerful set of tools and features for formalizing mathematical concepts and proofs. Isabelle/HOL includes a set of built-in proof methods and tactics, as well as a flexible type system and support for code generation.