This challenge is to build your own Brainfck Interpreter. Just in case you’re wondering, yes the should be a u, but Coding Challenges is family friendly so we’re avoiding the direct profanity (aka, my kids read Coding Challenges and will tell me off for it).
Lisp is a general-purpose, multi-paradigm programming language suited for a wide variety of industry applications. It is probably most widely know for being the programming language built into Emacs. As well as that it was used to build Hacker News (Paul Graham is a Lisp fan), Grammarly, Circle CI (actually using the modern dialect Clojure) and Boeing.