Final answer:
Global variables in programming languages are accessible throughout the entire program but can lead to complications in debugging and comprehending the code.
Step-by-step explanation:
Global variables in programming languages are variables that are defined outside of any function, class, or block of code. This means that they can be accessed and modified from any part of the program, which includes all the functions and blocks of code in a program. However, while they provide a convenient way to store information that can be accessed throughout a program, they also come with risks. Global variables can make debugging and understanding code more difficult, because any part of the program can change their values, which can lead to unexpected results if not managed carefully.