In C programming, macros are small pieces of code that can be executed with a single command. They can be used to automate tasks, simplify complex processes, and save time by reducing errors through automating repetitive tasks. A macro is defined by the #define directive, and whenever the compiler encounters a macro in a program, it replaces it with the macro value. Macros can be used to replace a piece of code with a single value of the macro, and there are three types of macros: object-like, function-like, and chain-like.

Macros are useful in C programming for several reasons, including:

• Performance: Macros can eliminate function call overhead because they are always expanded in-line, unlike functions.
• Customization: Macros can be customized to fit specific needs, allowing for greater flexibility in how tasks are completed.
• Consistency: Macros can help ensure consistency in tasks by following a set of predetermined instructions.
• Efficiency: Macros can help increase program efficiency by reducing the amount of code that needs to be written and executed.

Overall, macros are a useful tool in C programming that can help automate tasks, simplify complex processes, and save time by reducing errors through automating repetitive tasks.