Esoteric programming language also known as Esolang, it is a computer programming language designed to test boundaries and possibilities, experiment with strange ideas that are hard to program, they are done just for fun, rather than for practical use. One of the most well known esolangs are brainfuck, Befunge, piet and ook.
Esoteric programming languages are those designed to make a point about our language design, in many cases a kind of in-programming joke. These programmes are so varied that they are difficult to categorise. For instance, there is one that is designed just to output its source code. Another camouflages the real meaning of messages.
There are languages with a specific objective, such as bypassing a security system, others that create deliberately unusable languages. Another has artistic endpoints, while Befunge aimed to design a language for which it was as hard as possible to create a compiler. All this is very sophisticated stuff for the non-programmer individual and from that outsider point of view, it might seem that very skilled people are spending valuable time producing highly unusual work with dubious end resullts.