A recursive function call mechanism in C is when a function calls itself during its execution.

This process allows for solving complex problems by breaking them down into smaller, more manageable tasks. When a function calls itself, it creates a new instance of the function on top of the current one.

This new instance has its own set of local variables and parameters, separate from the previous one. The recursive function continues to call itself until a base case is reached, at which point the function starts returning values back up the call stack.

To understand it easily I have created an animation which would help you to grasp the concept. 

Understanding how the recursive function call mechanism works in C is crucial for implementing recursive algorithms and solving problems efficiently.