question about main function

These are very, very basic questions about the C language. This probably isn't the best forum to talk about it. This forum is here to discuss the particulars of the Tiva hardware and it's tools (like the C compiler). So it's going to be hard to explain everything.

Are you talking a class? The class should have some reference or prerequisite material on programming in general and the C language. There are plenty of books and a google search of "C Language tutorial" should find some online information to get you started.

main is the function all C programs use. It basically defines the start of the program.

STATUS = -1; 

sets STATUS variable to -1.

MStatus == -1

"Is the MStatus variable equal to negative 1?"

The == operator is a test for equality, while = is an assignment.

// Tcount is the number of clock cycles to delay
int32_t TotalDelay(int32_t Tcount)
{
	int32_t STATUS = 0;
	
	// Check to see if the number of clock cycles
	// is more than what SysTickDelay can accept.
	// consult the datasheet section 3.3 to see that it
	// is limited to 24 bits
	while (Tcount > MAXcount)
	{
		// Change the return status
		STATUS = -1;
		// Delay the maximum amount
		SysTickDelay(MAXcount);
		// Reduce the amount of clock cycles to wait
		// by how long we just delayed in SysTickDelay()
		Tcount = Tcount - MAXcount;
		// Now go back to the while() loop and check to see
		// if we need to loop again
	}
	SysTickDelay(Tcount);
	// This return status value does not make sense to me. Why
	// would the caller care if we had to loop?
	return (STATUS);	// Return 0, or -1 if we had to loop
}

Is this something you wrote? Is it working for you?