Misc
The miscellaneous category contains challenges not found in the other usual categories. Common types of challenges are jails and various programming/algorithm problems. Jails are programs that give the user some degree of control, with the goal to break out of the particular restrictions of the jail.
Pyjail
One common challenge format is the Python jail, or "pyjail" for short. These are Python programs that take input form the user and executes it directly as Python code in some form. Often times there will be restrictions on the Python code that is executed. See here for some ideas.
Other file formats
As a general tip, running the file
command on challenge files can tell you a lot of useful information. One file format in many misc challenges is the .wav format, which stores audio data with pulse-code modulation. In this format, audio waveforms are sampled at discrete intervals and are stored as a series of integers.