Answer 1

They have different uses based on context:

& can be a bitwise AND, and * can mean multiply, however I assume you mean in the context of pointers?

int i = 5;
increment("&i)

The above call to increment(), send the address of the integer variable i, as the second argument. C and C++ functions can't change the values of arguments sent to them, but they can change the value of an item, if that item's memory address is passed instead.

void increment(int* a)
{
// The *a here means 'work on the value
// at memory address 'a'
(*a)++
}

int i = 5;
increment(&i);

The above code will increment the value stored in i.

void no_increment(g)
{
g++;
}

i = 5;
no_increment(i)

i will not be changed.