Esoteric programming languages are designed as a proof of concept or as a joke. It is rarely meant to be usable. Nonetheless, these languages are Turing complete, this means that any program a general computer can run can be written in that language.
Without further ado, here are some of my favourite esoteric languages:
Here the language is composed of words from internet memes.
HAI CAN HAS STDIO? PLZ OPEN FILE "LOLCATS.TXT"? AWSUM THX VISIBLE FILE O NOES INVISIBLE "ERRROR!" KTHXBYE
The entire language consists of only spaces, tabs, and linefeeds. So the whole code is just blank. Pretty cool huh.
One of the best known esoteric language is Brainfuck and it is famously hard to read. It has just 8 commands.
Example for hello world:
>+++++++++[<++++++++>-]<.>+++++++[<++++>-] <+.+++++++..+++.>>>++++++++[<++++>-] <.>>>++++++++++[<+++++++++>-]<---.<<<<. +++.------.--------.>>+.
Here’s a visualiser for it.